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Concept Notes For Reading 5 - Time value of money
Reading Summary
This reading is the most important reading for the CFA Level 1 Examination as it covers the basics of
present value (PV) of the expected future cash flows. The PV concept is used throughout the curriculum
with major emphasis in Equity Valuation, Fixed Income valuation and corporate finance. A mastery of
time value is paramount to be successful in the examination.
The topic covers calculation of present value and future value for a single cash flow, a series of cash
flow (known as annuity), computation of effective rate, problems related to mortgages, retirement.
Understanding of time line is critical and it is advised that the candidates should draw the timeline while
solving any problems. For easy problems it might look that drawing time line is waste of time but
timeline is important when you are solving complex problems with multiple cash flows as the timeline
will give a perfect picture of the cash inflows and outflows.
Basic Idea and Concepts
Time Value of Money (TVM) links cash flow, interest rate, compounding frequency, time period and the
present value or the future value. TVM reflects that a $1 amount with a person today is more valuable
than $1 at a future date because $1 can be invested now and interest can be earned on the investment.
TVM would require calculation of Future Value (FV), which is result of compounding the investment at a
certain interest rate. TVM also entails finding the present value (PV), which is reverse of compounding
and is referred as discounting. Comparison of PV or FV is very useful in analyzing investments and then
making an investment decision. As an investor you would be more interested to invest in those
products which will fetch you more money in the future for the same amount invested today.
Usage of Financial Calculator
Solving TVM problems becomes very easy when you are using financial calculator. There are 2 types of
calculator permitted in the CFA Exam, one from Hewlett Packard and another from Texas Instruments.
We recommend Texas Instrument’s calculators because they are similar to the calculators that you have
used in the past and are easy to master.
In TI BA II Plus calculator you have a set of TVM Calculation Key. The following are the function keys
available for TVM calculation
N = Number of compounding periods FV = Future value
I/Y = Interest rate per compounding period PMT = Annuity payments, or constant periodic cash
flow
PV = Present value CPT = Compute
We will provide detail in some of the questions on the operation of the calculator.
Timeline
Timeline is a representation of the cash flows with respect to time. We follow a notation when drawing
a timeline
Cash Outflow – Any cash outflow is treated as Negative
Cash Inflow – Any cash outflow is treated as Positive
-$500 $200 $200 $200 $200
T=0 T=1 T=2 T=3 T=4
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In the timeline above, we have an initial investment of $500 being done and hence it is an outflow, that
is why we have taken the amount as -$500 in the timeline. Since the initial investment is done now, the
time has been put as T=0 in the timeline. Likewise we are getting a series of return every period from
the investment, since the amount of $200 is cash inflow to us, we have taken a positive sign for it. There
are four payments of $200 each received and hence we are displaying four payments in the time line.
Drawing a time line is a good idea to solve any TVM problem.
LOS 5.a. Interpret interest rates as required rate of return, discount rate or opportunity cost
There are three ways in which we can interpret the interest rates:-
1. Required rate of return is the return required by the investors to postpone their current
consumption to a future period.
2. Discount rate is the rate used to discount the future cash flows (that is the money to be received in
the future) to the current period. In essence discount rate and required rate are one and the same. We
use the term “discount rate” to bring a future cash flow to present period and the term “required rate”
to compound a current cash flow to future period.
3. Opportunity cost is the benefit that investors would have received if they had invested their money
in some other investment and they are investing in any other product of the same risk they should be
able to meet the opportunity cost. This can also be said as the value that investors forego by choosing a
particular investment. This would be clear from the following example:-
Suppose an investor has taken loan at the rate of 10% pa from a bank and is offered an opportunity to
invest in a product A which is promising a yield of 12%. Now the investor’s opportunity cost is 12%, he
would invest in any other product having same risk if the return from the other product is more than
12%.
LOS 5.b. Explain an interest rate as the sum of a real risk-free rate, expected inflation, and premiums
that compensate investors for distinct types of risk;
When there are no uncertainty and no inflation then the interest rate received by the investor is known
as Real Risk Free Rate. The risk free rate is observed in only the government bonds (also known as
treasury securities), however these are not real rate as there is some amount of inflation present. The
interest rate given by the government securities is Nominal risk free rate.
Here we bring the concept of inflation premium. When an inflation premium is added to real risk free
rate, the resulting rate is the nominal risk free rate. Following equation will make things clear
Or we can approximate the equation to;
Since we are in an uncertain world there are risks present in any investment, an investor should be
compensated for these risks, as a result the required return need to be increased by what is termed as
risk premium. There are three types of risk premium we will discuss in this topic, these are:-
Default Risk Premium is the premium added for the likelihood or the probability that the
borrower will not meet interest or principal payment on time and is likely to default on the
loan. When there is higher uncertainty the premium would be more.
Maturity Risk Premium is the premium that one obtains for parting away with his money for
longer period of time. Typically as the no of days of an investment increases, the investor is
being deprived of his wealth for longer time hence the investor should be compensated by way
of higher return. This higher return is attributed as maturity risk premium.
Liquidity Risk Premium is the premium provided to the investor for investing in securities
having low liquidity. Liquidity here implies how fast the asset can be sold in the market and
money received. Typically real estate investments give higher return because the investment is
not liquid, it may take months to sell a property and hence liquidity premium should be more.
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So, for an investor the required return on equity should be the approximately the sum of real risk free
rate and the various premiums.
Required rate = Real Risk Free Rate + Inflation Premium + Default Risk premium
+ Liquidity Risk premium + Maturity Risk premium
In Fixed Income study session 15, reading 61, we will come across other risk premiums that an investor
should consider when investing.
LOS 5.c. Calculate and interpret the effective annual rate, given the stated annual interest rate and the
frequency of compounding
Compounding is a concept in which interest accumulate over a period of time. A compounding period is
a period in which interest is accrued or accumulated; there can be different compounding period in a
year.
There are three ways in which we can quote the interest rate in a year
Periodic Interest rate – This is the interest rate that is applicable for a period, the period can be
1 month, 1 day, 1 year or anything. For example if the 6 months periodic rate is 5%, it means
that we will get return of 5% in 6 month.
Stated annual interest rate – This is also known as quoted interest rate. Here the interest rate
is stated annually, so for the example of the periodic rate given above, the stated annual rate
will be 5% multiplied by 2 or 10%.
Effective annual rate (EAR) takes the effect of compounding within a year. For a stated annual
rate, the higher the number of compounding the higher is the effective annual rate. EAR can be
stated as per the following formula
Where, periodic rate = Stated annual rate / Number of compounding period in a year
Continuous compounding is a concept in which there is infinite number of compounding period in a
year. The interest rate thus is called as continuous compounding interest rate.
For a continuous compounding rate, the EAR is given as
Where r is the stated annual rate
Concept Builder – Effective Annual Rate Computation - Single Computation
1. Find Effective Annual rate for a bank deposit, in which the stated interest rate is 8% per annum and
the frequency of compounding is semi-annually
Answer
Remember whenever we are computing effective annual rate, we need to find first the periodic rate.
Periodic rate = stated rate / number of periods in a year
Periodic rate = 8%/2 = 4%
EAR = (1.04)2 -1 = .0816 = 8.16%
Concept Builder – Effective Annual Rate Computation – Understanding increasing frequency
2. For a bank deposit, the stated interest rate is 12% per annum compounded monthly?
Find the Effective Annual Rate (EAR), for the following compounding frequency
a) Semi-annually b) Quarterly c) Monthly d) Daily e) Continuously
Answer
a) When the compounding is semi-annual => EAR = (1.06)2 – 1 = 12.36%
b) When the compounding is quarterly => EAR = (1.03)4 – 1 = 12.5509%
Calculator TIP: Press 1.03 ; then press yx function key (present above 9), now press 4
You have computed 1.034 ; now you press -; then press 1; then multiply by 100 to get the rate
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c) When the compounding is monthly=> EAR = (1.01)12 – 1 = 12.6825%
d) When the compounding is daily=> periodic rate = 12%/365 = 0.032877%
EAR = (1.000329)365 – 1 = 12.7475%
e) The EAR for a continuously compounding rate is – ; please note that r is the stated rate
EAR = –
Calculator TIP: Press 0.12; then Press 2nd; then press LN (present on the left side of 7); this will
compute ; now subtract 1; after this multiply by 100.
Now, the stated rate was 12%, as we increase the number of compounding, you can see that the EAR is
increasing, this is primarily because as the compounding period increases, the more interest is earned
on the interest, so it results in higher effective rate.
The highest possible effective interest rate would be achieved when continuous compounding is done.
LOS 5.d. Solve time value of money problems when compounding periods are other than annual;
When compounding periods are not annually then we must take into consideration that the number of
period will be more than 1. Also we need to adjust the periodic rate to reflect this.
As a thumb-rule, if there are m periods in a year and there are n years, then we should divide the
interest rate by m and multiply the number of years by m.
For example, if we are required to solve for a problem in which the stated rate is 8% pa, with quarterly
compounding and 5 years, we should have the periodic rate as 2% and the number of periods as 20.
Concept Builder – Finding Future Value when compounding period is more than annual
3. Canara bank is offering interest rate of 9.15% for fixed deposits for 2 years. The compounding is
quarterly, how much amount would you receive at the end of the period, if you deposit $1000.
Answer
There are 2 approach to solve problems of this kind
1. Find EAR and then find the FV using the compounding for multiple years
Periodic rate = 9.15%/4 = 2.2875%
EAR = (1.022875)4 – 1 = 9.4688%
FV = PV( 1 + EAR)N
So the amount after 2 years will be equal to = 1000 * 1.0946882 = $1,198.3412
2. Solve directly using the calculator
Here FV = ?
PV = -$1000 (Note –ve sign) ; PMT = 0 ; I/Y = 9.15/4 = 2.2875; N = 2 * 4 = 8
FV = $1,198.34
Calculator TIP: First Press 2nd ; Press FV; this will clear the previous TVM calculation
For PV: Press 1000; Press +|- (placed right of decimal); Press PV => PV = -1000
For PMT: Press 0; Press PMT => PMT = 0
For I/Y : Press 2.2875 ; Press I/Y => I/Y = 2.2875
For N: Press 8; Press N => N = 8
Now to find out FV; Press CPT (top left corner); Press FV => You will get FV = 1198.3412
Concept Builder – Finding Present Value when compounding period is more than annual
4. How much money should you deposit now in your investment account to get $1000 after 3 years.
Assuming that the investment account offers a return of 10%, compounded semi-annually?
Answer
As we have seen in the above example, its easier to use the TVM function of the calculator to solve
these kind of problems, we will use the TVM keys to solve it.
First we need to identify the values associated with the TVM Keys.
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Here, FV = 1000; PV = ? ; N = 2 * 3 = 6; I/Y = 10/2 = 5; PMT = 0
So we need to input these values in the calculator to find out the answer
The answer would be -$746.21, the negative sign implies that an amount of 746 goes out from you
(outflow) in the investment account.
Calculator TIP: First Press 2nd ; Press FV; this will clear the previous TVM calculation
For FV: Press 1000; Press FV => FV = 1000
For PMT: Press 0; Press PMT => PMT =0
For I/Y : Press 10; Press ÷ ; Press 2; Press =; Press I/Y ; Press I/Y => I/Y = 5
For N: Press 8; Press N=> N = 8
Now to find out PV; Press CPT (top left corner); Press PV => You will get PV = -746.21
LOS 5.e. calculate and interpret the future value (FV) and present value (PV) of a single sum of money,
an ordinary annuity, an annuity due, a perpetuity (PV only), and a series of unequal cash flows;
Future value is the money to be received at a later date. We have the following formula for the Future
Value for a single cash investment. We assume that the interest generated is also invested at the given
rate.
Concept Builder – Future Value of a Single Sum
5. How much would my term deposit of $1000 will become in 7 years, if the bank is offering me 10%
interest rate compounded annually?
Answer
This is similar question like Concept Builder # 3; only thing here is that the compounding period is
annual.
We can solve this using the calculator as shown in the #3. But whenever you see a single cash flow, its
much simpler to use the formula directly than using calculator.
FV = PV (1 + I/Y) N => FV = 1000 * (1.1)7 = $1948.7171
So, if you invest $1000 now, you will get $1948.71 after 7 years.
Present Value is the money that you can assume to be equivalent of the future cash flows. The present
value of the expected single future cash flows is given by
• FV = future value at time n
• PV = present value
• I/Y = interest rate per period
• N = number of periods
Concept Builder – Present Value of a Single Sum
6. How much would be the present value of an investment which promises to return $1000 in 7 years,
the required rate of return is 10%?
Answer
This is similar question like Concept Builder # 4; only thing here is that the compounding period is
annual.
We can solve this using the calculator as shown in concept builder #4. But whenever you see a single
cash flow, its much simpler to use the formula directly than using calculator.
PV = FV/ (1 + I/Y) N => PV = 1000 / (1.1)7 = 513.158
Calculator TIP:
First Find 1.17 => Press 1.1; Press YX; Press 7; => you will get 1.17; which is 1.948717
Now, Press button (above YX) => you will get 0.513158
Now, press X; press 1000; press =; You will get $513.158 (which is the present value)
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Perpetuity is a concept in which same cash flow is received for an indefinite (infinite) number of periods
in the future. Present value of perpetuity is what the infinite cash flow should be worth now.
PV of Perpetuity = Cash flow / Required rate of return
Or
PV of perpetuity is used in the valuation of preferred stock.
Preferred stock is a financial product which gives a constant dividend till perpetuity. Value of preferred
stock is given by
Concept Builder – Present Value of a Perpetuity
7. Tata motor has issued a preferred stock, which pays an annual dividend of $10. If an investor’s
required rate of return is 10%, how much the preferred stock would be valued by that investor?
Answer
Price of preferred stock would be the same as the present value of the dividends that it is paying.
Since, preferred stock is a perpetuity, we will be calculating the present value from its formula.
PV = D/r
PV = $10/0.1 = $100
So, the price at which the preferred stock should sell will be equal to $100.
Concept Builder – Required rate of return of a perpetuity when PV is given
8. A preferred stock is trading at a price of $120 per share. The preferred stock pays annual dividend
of $8. What is the required rate of return for the preferred stock?
Answer
In this problem, we know the price and the dividend that it is paying, the required rate of return can be
calculated using the formula of PV of preferred stock.
PV = D/r => r = D/PV => required rate = $8/$120 = 6.67%
Annuities – Sometimes we do not invest the money in lump-sum only. We invest regularly, so this is the
concept of annuity. The regular period can be annually, quarterly, monthly or daily.
Present Value of Annuity is the sum that you can receive now in lieu of the future cash flows.
Future Value of Annuity is the sum that you will receive in the future for the investments that
you are doing periodically.
You need not remember the formula of the perpetuity, we should use financial calculator to solve
perpetuity problems. You will be explained in the class and the video as to how to apply the concept.
There are 2 types of annuities
Ordinary Annuity – In ordinary annuity the investment is done at the end of the period. So if you
are buying a product on 1st January 2010 and the product is annual pay then first payment will be
done on 31st December 2010. If the product matures in 5 years then you will make the last payment
on 31st December 2014 and also receive the maturity value on 31st December 2014.
Annuity due – In annuity due the investment is done at the beginning of the period. So if you are
buying a product on 1st January 2010 and the product is annual pay then first payment will be done
on 1st January 2010. If the product matures in 5 years then you will make the last payment on 1st
January 2014 and receive the maturity value on 31st December 2014.
So, in both the case we are receiving maturity value on 31st December 2014, but in ordinary annuity
the last payment is not earning any interest, hence the Future Value will be lesser than that of the
annuity due.
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Concept Builder – Present Value and Future Value of Ordinary Annuity
9. I have invested in an ordinary annuity product; the annual payment is $1000 for a total of 10
payments. First installment will start after 1 year from today, how much is the PV of this? How
much it will become at the end of 10 years? Interest rate on this product is 8%.
Answer
We would be solving all the problems in which there are intermediate cash flows using the financial
calculator. You should be able to identify the value of any 4 of the 5 functions of TVM. One unknown
value can be easily found out from calculator.
NOTE: For the Ordinary Annuity; we use the END Mode in the calculator.
For Computing PV – PV is unknown
Here, PMT = -$1000; N = 10; I/Y = 8; FV = 0; PV =?
Why is FV zero here? – Please note that when you are calculating PV, assume that FV is zero and vice
versa. The PMT and N is taking care of the amount of cash that is being deposited.
Please see the timeline for this below
So, using financial calculator, we will input the values for the various parameters and then compute FV.
CPT -> PV will give the present value; PV = $6,710.08
For Computing FV – FV is unknown
Here, PMT = -$1000; N = 10; I/Y = 8; PV = 0; FV =?
CPT -> FV will give the future value; FV = $14,486.56
Concept Builder – Using Annuity Concept to Value a Bond
10. A bond having face value of $100 is paying annual coupon, the coupon rate is 10%. The bond has 5
years to maturity. If the current market interest rate (required rate) is 6%, then at what price the
bond should sell in the market?
Answer
Face value of a bond is the amount that we receive at the maturity of the bond. So face value equals the
future value that is received from an investment in bond.
The coupon payment is calculated on the face value. So a bond having coupon rate of 10% will given
coupon equal to 10% * Face value = 10% * $100 = $10, coupon can be regarded as the PMT.
The bond pays the first coupon at the end of the period, so a bond valuation can be thought of as
Ordinary Annuity.
For an annual pay bond, the years to maturity will be the number of payment made. For bonds with
semi-annual coupon, the number of period will be twice the number of years to maturity and coupon
would be half of the annual coupon.
The market interest rate can be thought of as required rate or I/Y.
So, for this bond valuation, we have the following parameters
N = 5; I/Y = 6; PV = ? ; PMT = $10; FV = $100
© Knowledge Varsity – 2011
Please note that as an investor, we will receive the coupon and also the face value, and hence as per
our sign convention, both of these should be Positive.
CPT -> PV = -$116.849
The negative sign means, that you will have to pay $116.849 to buy the bond.
This is how the bonds are valued and this would be used in Financial Reporting and Fixed Income
Valuation.
Concept Builder – Present Value of Ordinary Annuity, when the first payment is at a later date
11. My grandfather will give me $1000 for 6 years when I become 18 years old. I have just completed
15 years. My required rate of return is 10% p.a. How much is the present value of my grand pa’s
gift?
Answer
Please see the timeline below, I will receive the first payment of $1000, when I will become 18 years.
Since there are total of 6 payments, I will get the payment till age of 23 (and not 24)
For ordinary annuity or In END Mode, the following point need to be imprint in your mind
1. The PV is one period before the first payment day
2. The FV is on the last payment day
If we calculate the present value from the calculator, it will give us the present value at T = 17 and not
at T = 15, which is our requirement.
So, this problem involves 2 steps. First find out the present value using the calculator, it would come at
T =17 and then discount this for 2 more periods to arrive at the present value at T=15.
1st Step: N = 6; I/Y =10; PV = ? ; PMT = 1000; FV = 0
CPT -> PV = -$4,355.26 ; Please note that this is PV at T =17
2nd Step: PV (at T = 15) = PV (at T =17) / (1+r)2
PV15 = PV17/(1+r)2 => 4355/1.12 => $3,599.38
So, the present value of the payment is $3,599.38
Concept Builder – Present and Future Value of Annuity due
12. I have invested in annuity due product of installment $1000 per year for 10 payments. First
installment started today, how much is the PV of this? How much it will become at the end of 10
years? Interest rate on this product is 8%.
Answer
COMPUTATION OF Present Value.
See the timeline of this problem below, pay attention here, the first payment is being done at T=0 and
there is no payment done at T=10, the last payment was done at T= 9.
There are 2 approach to solve such type of problems
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A. Using our financial calculator in Begin Mode
B. Using our financial calculator in End Mode (Ordinary annuity mode) & then making adjustment
First using the Begin Mode.
Please change the mode in your calculator by performing the following functions
Press 2nd; Press PMT; Press 2nd ; Press ENTER – You will begin seeing BGN in your calculator, it shows
that your calculator is now in begin mode.
In BEGIN Mode, the following point need to be imprint in your mind
1. The PV is on the first payment day
Now, with begin mode set, it is a simple problem. You just need to enter the parameters like the way
you had entered in concept builder #9
Here, PMT = -$1000; N = 10; I/Y = 8; FV = 0; PV =?
CPT-> PV => PV = $7246.88
So, the present value of the investment is $7246.88
Using the other approach : The problem can be solved using the end mode also. Since your calculator is
in Begin Mode, you need to change it to END Mode. The steps to do this is same as the way we
changed to begin mode
Press 2nd; Press PMT; Press 2nd ; Press ENTER – You will begin seeing END in your calculator, it shows
that your calculator is now in END mode.
When the calculator is in END mode, we had observed that the present value is 1 period before the
first payment.
So here the PV will come at T =-1. See the timeline below.
But we need to find out the value at T =0 and not at T = -1, so what we need to do is to find out the PV
at T =0 from the value we obtained at T = -1
PV (At T = 0) = PV (At T = -1) * (1+r)
Or, we can say that PV(Annuity Due) = PV(Ordinary Annuity) * (1 + r )
Here, PMT = -$1000; N = 10; I/Y = 8; FV = 0; PV =?
CPT-> PV => PV = $6710.08
This PV is at T=-1
=> PV0 = PV-1 * (1+r) => PV0 = 6710.08 * 1.08 = $7246.88
So, the value of PV is same in both the case.
COMPUTATION OF Future Value.
Here also, we have the same 2 approach to solve the problem.
First we will solve using the BEGIN Mode.
In BEGIN Mode, the following point need to be imprint in your mind
1. The FV is one period after the last payment day
We will change the mode from END To BEGIN, using the steps highlighted earlier.
Please change the mode in your calculator by performing the following functions
Press 2nd; Press PMT; Press 2nd ; Press ENTER – You will begin seeing BGN in your calculator, it shows
that your calculator is now in begin mode.
© Knowledge Varsity – 2011
In the Begin mode, the timeline looks like below.
So, we will enter the value and find out the future value.
Here, PMT = -$1000; N = 10; I/Y = 8; FV = ?; PV =0
CPT-> FV => FV = $15,645.48
Secondly, we will solve the problem using the END Mode
Since your calculator is in Begin Mode, you need to change it to END Mode. The steps to do this is same
as the way we changed to begin mode
Press 2nd; Press PMT; Press 2nd ; Press ENTER – You will begin seeing END in your calculator, it shows
that your calculator is now in END mode.
When the calculator is in END mode, we had observed that the Future value is on the last payment.
So here the FV will come at T =9. See the timeline below.
But, we want the FV at T=10
So, we can arrive at the FV at 10, by compounding the FV at 9
FV10 = FV9 * (1+r)
So, we have a new rule => FV(Annuity Due) = FV(Ordinary Annuity) * (1 + r )
So, we will enter the value and find out the future value.
Here, PMT = -$1000; N = 10; I/Y = 8; FV = ?; PV =0
CPT-> FV => FV9 = $14,486.56
We know, FV10 = FV9 * (1+r) => FV10 = $14,486.56 * 1.08 = $15,645.48
So, the answer is the same as it was obtained from the Begin Mode.
IMPORTANT
So, whenever we are asked to calculate the PV or FV of annuity due, we can solve using the default END
Mode. We advise you to follow this approach, because in exam, if you forget to change the mode then
it would be problematic for you, since most of the questions would be end mode questions.
Things to Learn
In END Mode
1. The PV is one period before the first payment day
2. The FV is on the last payment day
In BEGIN Mode
1. The PV is on the first payment day
2. The FV is one period after the last payment day
© Knowledge Varsity – 2011 Page 11
Concept Builder – Future Value at a later date of Annuity due
13. I am making an investment of $100 every year, starting from now for a total 3 payments. How much
money I will receive at the end of 6 years? The interest rate of the investment is 10%.
Answer
First you need to make timeline for this particular problem, which is given below
We would be using our calculator in END MODE
In the END Mode, if we are computing the FV, it would come at T=2
Now, we should compound the value received at T=2 to get the FV at T=6. Since there are 4 periods in
between, we can write
FV6 = FV2 * (1+r)4
Plugging in the values in the financial calculator
Here, PMT = -$100; N = 3; I/Y =10; PV =0; FV = ?
CPT-> FV => FV2 = $331
FV6 = $331 * (1.1)4 = $484.617
So, I will receive $484.6 at the end of 6 years.
Concept Builder – Present and Future value of cash flows when the cash flow is not same
14. Find the present value and the future value for the following cash flows. Required rate of return is
10%.
Answer
Since, the TVM functions assume that the PMT remains the same, we can’t use TVM here. We should
use the Cash Flow function here.
You will find, a button named CF in the 2nd row, 2nd Column.
Whenever we are calculating using CF, we should first clear the memory.
To Clear Memory – Press CF; Press 2nd; Press CE|C
You will observe CF0 on the screen, it is asking for the Cash flow at T=0
For CF0: Press 1000; Press +|- ; Press ENTER; Press ↓
You See CF1: Press 2000; Press +|- ; Press ENTER; Press ↓
You see F01 => By default its value is 1 in the calculator. This is the concept of frequency, it is asking you
how many times -2000 is coming consecutively in the problem. Since -2000 is coming consecutively
only once, we will leave F01 at 1 only and press the down arrow ↓ to move to C02.
You see C02: Press 3000; Press +|- ; Press ENTER; Press ↓↓ (Yes 2 times, as the frequency of -3000 is
also 1)
You see C03: Press 2000; Press +|- ; Press ENTER; Press ↓
Now, the data is entered, we will calculate the PV.
Note that, for CF function, there is a button to calculate NPV.
NPV is Net Present Value and is equal to PV of Inflows – Outflows , but for this NPV will be same as the
PV.
© Knowledge Varsity – 2011
Press NPV; You will see I in the screen, Press 10; Press ENTER; Press ↓; You will see NPV on the screen;
Press CPT
NPV = -6800.15
For finding out the future value, you can assume that you are investing 6,800 for a period of 4 years.
FV = 6800 * 1.14 => FV = $9,956.1
LOS 5.f. Draw a time line and solve time value of money applications (for example, mortgages and
savings for college tuition or retirement).
As mentioned, we can solve various type of problems by employing time value of money calculation and it is better to draw a timeline before solving the problem. This LOS covers the application of TVM concepts in real life. We will cover this LOS through examples and understand the various applications. Concept Builder – Calculation of I/Y
15. You have deposited $100 in the account today, after 7 years, the amount would become $200, what
is the stated annual rate if the compounding is annual?
Answer
Here we need to calculate the rate or I/Y
The parameters of TVM are :
FV = $200; PV = -$100; N = 7; PMT = 0; I/Y = ?
CPT -> I/Y => I/Y = 10.4%
Concept Builder – Calculation of PMT
16. You are required to deposit a fixed amount every year in your investment account starting from the
end of this year. If the stated rate is 10% p.a. and you are depositing for a total of 10 years, you will
receive an amount of $100,000. How much amount you should deposit every year?
Answer
Here we need to calculate the amount deposited every year or PMT
Note that there is no money in the account today, it is a case of ordinary annuity since the money is
deposited at the end of the period.
The parameters of TVM are :
FV = $100,000; PV = $0; N = 10; I/Y =10; PMT = ?
CPT -> PMT => PMT = -$6,274.5
So, you need to deposit 6,274.5 every year to get $100,000 at the end of 10 years.
Concept Builder – Calculation of Number of Periods
17. You are shown an investment plan that will require depositing every year $10,000 starting from the
end of this year; it is promised that at the end you will get a sum of $115,000. If the interest rate
offered by the investment plan is 10.15%, then find out for how many years you will have to deposit
the money in the plan?
Answer
Here we need to calculate N
The parameters of TVM are :
FV = $115,000; PV = $0; PMT = -$10,000; I/Y =10; N= ?
CPT -> N => N = 8.03
So, you need to deposit the amount for 8 years.
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Concept Builder – Compounded Annual Growth Rate
18. Tata Steel’s EPS was $5 in 2002, In year 2008 the EPS was $14. Find the compounded annual growth
rate (CAGR) of the EPS.
Answer
CAGR is the rate at which the EPS has grown.
Please see the timeline below
Easily we can solve this with the financial calculator
So, the number of periods from 2002 to 2008 is equal to 6, therefore N = 6
The parameters of TVM are :
FV = -$14; PV = $5; PMT = 0; N=6; I/Y =?
CPT -> I/Y => I/Y = 18.72%
So, the EPS has grown at an average rate of 18.72% for the 6 years.
Concept Builder – Loan Calculation
19. I took a housing of $200,000 for 15 years; the rate of the loan is 10%. Calculate
A. How much monthly payment I am doing.
B. How much is the principal payment done in 1st month?
C. How much is the principal remaining after 60 installments.
Answer
This is another set of problem, where you will find financial calculator handy.
Please note that housing loan is an amortizing loan, where both principal and interest is paid in the
monthly payment that is being done. At the end of the loan term, there is no money that is required to
be paid to the bank, so the future value is 0.
For Part A – It is just asking for the EMI that I am paying and hence we need to find the PMT
The parameters of TVM are :
FV = 0; PV = $200,000; I/Y =10/12 = 0.833; N=15 *12 = 180; PMT =?
CPT ->PMT => PMT = -2,149.21
So, every month, you should pay $2,149.2 towards your housing loan
For Part B –So, for the 1st month, we can calculate the interest that is accrued on $200,000 for 1 month
using the simple interest formula
Interest for the 1st month = PRT/100 => ($200,000 * 10 * 1 )/(12 *100) = $1,666.67
Out of the EMI of $2,149.21 ; $1667.67 is towards the interest charge
The principal payment = $2,149.21 - $1667.67 = $482.54
For Part C – This is a difficult question if you think conventionally, here you need to think Out Of Box, to
answer it in a simple manner. Think, if everything was as planned, you were paying the EMI and now 60
months are left. Can I say, that if you approach the bank after 60 months for a loan, they should give
you an amount which will be paid off by the end of 120 months, So we can say that whatever the
principal is remaining, should be equal to the loan amount that you would be given after 60 months.
To solve, this now your N = 120
FV = 0; I/Y =10/12 = 0.833; N=120; PMT =-2,149.21 ; PV = ?
CPT-> PV =>PV = $162,633.24
Since you have financial, these things are much easier to solve. Your calculator has AMORT Function,
which can be accessed by pressing 2nd and then Pressing PV.
Once you do that, you will find P1 on the screen.
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P1 is the point from which we want to calculate the principal payment/interest payment etc.
If you press ↓; you will find P2.
P2 is the point till which we want to calculate the principal payment/interest payment etc.
For Part B – we can solve using P1 = 1 and P2 = 1 , since we are interest for the principal payment for
the 1st month only.
Calculator TIP: Press 2nd; Press PV; You will see P1; Press 1; Press ENTER; Press ↓; You will see P2;
Press 1; Press ENTER;
Press ↓; You will See BAL => this is the Principal Remaining after P2
Press ↓; You will See PRN => this is the Principal paid between P1 and P2 => $482.54
Press ↓; You will See INT => this is the Interest paid between P1 and P2
For PART C – Using the financial calculator
P1 = 1; P2 = 60 (as we are interested in finding the principal remaining after 60 months)
Calculator TIP: Press 2nd; Press PV; You will see P1; Press 1; Press ENTER; Press ↓; You will see P2;
Press 60; Press ENTER;
Press ↓; You will See BAL => this is the Principal Remaining after P2 = $162,633
Press ↓; You will See PRN => this is the Principal paid between P1 and P2 => $37,366.76
Press ↓; You will See INT => this is the Interest paid between P1 and P2 => $91,585.85
So, in first 60 months, I have paid $91,585.85 as the interest and $37,366.76 as the principal.
Concept Builder – Retirement Calculation
20. An investor, plan to retire at the age of 60. He expects to live till the age of 90. He is currently aged
25. He invests the first payment in the account today and invest for 35 years (that is total of 35
investment done). The retirement account earns 12% per annum. Assume that he would like to
withdraw $30,000 per year starting from the point when he turns 60 for 30 years, find out the
amount he should deposit in his retirement account every year? Here assume, that the investor
doesn’t leave any money for his heirs.
Answer
This is a complex problem involving 2 series of cash flows. It’s good to draw a timeline to solve the
problem
In these type of problems, we need to come up with a common point.
If we take the middle point as common point, that will be the best.
So, we can find out the PV of the cash inflows at T = 59; Using that, we can find out the PV at T=60; and
then we can compute the PMT for the series of cash outflows.
Lets do step by step calculation
Step 1: Find out the PV at T = 59
Keep the calculator in the END mode, the 2nd series of cash flows from T=60 to T=89 looks like ordinary
annuity and the PV will come one period before the first cash flow.
FV = 0; I/Y =12; N=30; PMT =$30,000; PV = ?
CPT-> PV => PV = $241,655.19
Step 2: Find out the PMT. Here you have to note that the FV of the investment would be equal to the
© Knowledge Varsity – 2011 Page 15
present value that we have found out.
FV = PV59 = $241,655.19; PV = $0; N = 35; I/Y =12; PMT = ?
CPT -> PMT => PMT = -$559.82
So, the investor need to deposit $559.82 every year for 35 years, in order to get $30,000 every year
when he retires.
Experience, the power of Compounding, the investor is depositing only $560 and is able to withdraw
$30,000 per year.
If the investor, delays his investment by 5 years, that is the first payment , he does at the age of 30, then
he would be required to deposit $1,000 to experience the same inflow during retirement.
So, it’s always advisable to start the investment early.
© Knowledge Varsity – 2011
Concept Notes For Reading 6 - Discounted Cash Flow Applications
Reading Summary
This topic is another one which is relevant across the CFA Curriculum. In recent times, CFA Institute has
started asking questions on the concepts in this chapter and it might happen that you may be getting
questions on some of these topics. The calculation of cash flow using financial calculator will be covered
in this topic, however the same would be used in Corporate Finance and Equity Valuation. You should
be thorough with the Cash Flow function of your calculator. The return concepts of Time Weighted and
Money Weighted Returns may be intimidating for some to start with, but these are essential concepts
for any person in the investment industry. Lastly you are expected to understand some other return
measures which are kind of industry convention and are popular because of their simplicity. You should
solve all the questions that are given in this book as well as the problems that are there in the institute
book then only a clear-cut understanding of this chapter will emerge.
LOS 6.a. Calculate and interpret the net present value (NPV) and the internal rate of return (IRR) of an
investment
Companies take up projects as part of their business activity, typically a project requires upfront
investment (a cash outflow) and then subsequently companies benefit in the form of cash inflow. For a
company to undertake a project, not only the amount of return it is getting should be more than the
investment being done but also the company should be able to earn a decent rate of return on the
investment. To make investment decisions companies evaluate projects on the basis of NPV and IRR.
NPV or Net Present Value of an investment is its present value of the expected cash inflows minus the
present value of its expected cash outflows.
IRR or Internal Rate of Return is the discount rate which would make the NPV of a project equal to
Zero.
NPV Calculation Process – NPV of any project involves the following steps
1. Identify all the cash inflows and outflows
2. Determine the discount rate that should be used to discount these cash flows. In this section we
need not calculate the discount rate ourselves, when we cover the corporate finance section,
we will understand how to compute the rate.
3. Using the discount rate computed in step 2, find out the present value of cash outflows and
cash inflows. We as per our convention treat outflows as negative (hence they decrease NPV)
and treat inflow as positive (hence they increase NPV)
4. NPV is the summation of all the present value of the cash flows computed above. Please note
that since we are abiding by the sign convention, hence we need to just do the addition.
NPV Formula:
CFt : Cash flow in time period t
N : the number of periods for which investment is made
r : the discount rate used for finding out the present value
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Concept Builder – NPV and IRR Computation
1. Compute the NPV of a project which requires initial investment of $10 million. The cash flows are
expected to be $6 million in year 1, $5 million in year 2, $4 million in year 3 and $3 million in year 4.
The discount rate for the investment is 15%.
Answer
NPV:The NPV of the project can be calculated by discounting the cash flows.
NPV = -$10 + $5.217 + $3.780 + $2.630 + $1.715
NPV = $3.343 million
It is better to compute the NPV using financial calculator, the usage of TI BA II Plus will be discussed in
the classroom and also in the Pre-class content.
IRR: Computation of IRR is difficult manually and should be done using financial calculator only. There is
IRR function in the calculator which will be able to derive the IRR, please note that when discounted at
the IRR rate, the NPV will be equal to Zero.
The value of IRR = 32.9783%
LOS 6.b. Contrast the NPV rule to the IRR rule, and identify problems associated with the IRR Rule
In any investment the idea is to generate more wealth than what you have invested or produce a return
which is more than the cost of capital or required rate of return.
Typically the projects can be classified under the following
1. Independent Projects – When acceptance or rejection of a project does not affect the acceptance
or rejection of other projects then the projects are considered as independent projects. As an
example suppose a firm is considering investment in a new printer and investment in a vehicle,
these can be considered as two independent projects if the company has fund to buy both and the
company is evaluating these two investments as per their cash flow.
2. Mutually Exclusive Projects – Typically companies do not have high amount of capital and most of
the times it becomes necessary to take up only one project out of two, due to capital constraints. In
such case we say that the projects are mutually exclusive. For example if the firm has money either
to install printer or to buy the vehicle but not for both then it becomes important for the firm to
identify the project which will be more beneficial.
To evaluate any investment decision we have the following two rules
1. NPV Decision Rule: If a project is yielding positive value to the firm then the project is a good
project and it should be accepted. We can summarize this decision rule
a. Accept projects which have positive NPV as these projects are adding to the shareholder
wealth
b. Reject project having negative NPV as these projects are destroying the shareholder wealth
c. In case of mutually exclusive projects, select the one which has higher NPV. Mutually
exclusive projects are those projects in which only one can be selected, naturally the higher
NPV project is increasing the shareholder wealth more and hence we should accept that
project
2. IRR Decision Rule: The decision rule based on IRR helps in evaluation of how much return is being
generated.
a. Accept projects whose IRR is more than the required rate of return
b. Reject those whose IRR is less than the required rate
c. Unlike the NPV decision rule here we can’t say directly that in case of mutually exclusive
project we should accept project having higher IRR. This is because of certain problems with
the IRR method
© Knowledge Varsity – 2011
Problems Associated with the IRR Rule
Before we take up the problems with the IRR rule, first we need to understand that NPV and IRR would
give the same result for the independent projects. This is because
If NPV > 0 then IRR should be more than the required rate of return
If NPV < 0 then IRR should be less than the required rate of return
However for mutually exclusive projects (let’s say projects A &B) there can be conflicting results, that is
the NPV rule may result in selection of project A whereas IRR may result in selection of project B.
This conflict happens because of the following problems
1. Reinvestment–The calculation of IRR assumes that all the cash flows are reinvested at the IRR rate.
For example if a project has IRR of 20%, then it is assumed that the cash inflows which are expected
would be re-invested at 20% rate. Now many times it might happen that the firm is not able to find
lucrative investments and hence it might not be able to re-invest those cash flows at IRR rate, let’s
say that the firm is reinvesting those cash flows at a rate of 15% then the actual return from the
investment would be lower than the 20% which was estimated earlier. We will be covering this
concept in the Fixed Income in detail.
2. Timing – Another reason for conflict is the timing of the cash flows, one project may produce higher
cash flows during the early periods and another project may have higher cash flows in the later part
of the project.
3. Initial Investment –Conflicting results can be observed in cases where one project requires smaller
investment and produce smaller amount of cash flows compared to another project which require
more investment and produces higher cash flows.
You can remember these through the acronym RTI (Right to Information)
Concept Builder –NPV and IRR Rule Conflict
2.There are two mutually exclusive projects which have the following cash flows
Project A: CF0 = -$10,000; CF1 = $20,000
Project B: CF0 = -$40,000; CF1 = $60,000
The required rate of return is 10%. Which project should be selected and why?
Answer
Compute the NPV and the IRR of each of the project using the financial calculator
Project NPV IRR
A $8,181 100%
B $14,545 50%
If these were independent projects then both the project should have been selected because the NPV is
greater than 0 or IRR is more than the required rate of return.
However since the projects are mutually exclusive, we should select one of these projects. In case of
mutually exclusive projects we should compare the NPV and the project having higher NPV should be
selected, hence project B should be selected.
LOS 6.c. Define, calculate, and interpret a holding period return (total return)
Holding Period Return (HPR) is the return that is generated over the holding period. The holding period
can be any period; it can be a minute, several hours, many days or years, please do not confuse holding
period as yearly period. Here we are interested in determining the total return which means that the
return does not only include the change in the investment value but also include any cash flow that is
generated by the investment within the holding period. These cash flows which are generated are
called as intermediate cash flows. Stock investment has intermediate cash flow in the form of dividend
and bond investment results in coupon payment.
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Where for an equity investment
P1 is the price at the end of the period
P0 is the price at the end of the period
D is the dividend received
Concept Builder –Holding Period Return
3. An investor purchased a share for $20 and sold it at $22 after 6 months, also he received a dividend
of $0.5 just before he sold the share. Find his holding period return?
Answer
Ending Value of investment = $22
Beginning Value of investment = $20
Dividend received = $0.5
HPR = (22- 20 + 0.5) / 20 = 2.5/20
HPR = 12.5%
Concept Builder –Holding Period Return
4. A t bill priced at $98 with face value of $100 and 180 days until maturity. Find the holding period
return for the T bill?
Answer
Ending Value of investment = $100
Beginning Value of investment = $98
HPR = (100- 98) / 98 = 2/98
HPR = 2.0408%
LOS 6.d. Calculate, interpret, and distinguish between the money-weighted and time-weighted rates of
return of a portfolio, and appraise the performance of portfolios based on these measures
Money Weighted Return(MWR) – It is actually the internal rate of return for an investment. All the
deposits in the investment account are treated as cash inflow and all the withdrawals are treated as
cash outflow. After determining the inflow and outflow, IRR is calculated. This calculation is similar to
the calculation that we had done in Example 1.
Time Weighted Return(TWR)– It is actually the Geometric mean return of an investment. For
calculation of TWR we need to divide the investment horizon into several periods. The period for the
return calculation is computed whenever there is a major inflow or outflow from the portfolio. The
geometric mean of all the periodic returns is then calculated to find the time weighted return.
If there are N holding periods, the TWR can be calculated as follows
(1 + TWR)N = (1+ HPR1)*(1+ HPR2)*(1+ HPR3)* …….. (1+ HPRN)
Where HPRi is the Holding Period Return in the ith period
Concept Builder –Money Weighted Return and Time Weighted Return
5. An investor purchased one share of Goldman Sachs (GS) at $100 at T = 0, he again purchased one
more share of GS at $120 at T =1. He received total dividend of $2 at T= 1 and a dividend of $3 per share
at T =2, the investor sold the shares at T=2 for a total consideration of $260. Find money weighted and
time weighted return?
Answer
Important assumption : We assume that the dividend is paid just before the period ends.
Money Weighted Return Calculation:
Step 1 : We should identify the cash flows that are happening at the various intervals. As per our sign
convention, money going out from investor should be treated as negative and money coming to an
© Knowledge Varsity – 2011
investor should be treated as positive.
At T =0 : Purchase of 1st share was done => Cash outflow of $100 => CF0 = -$100
At T =1 : Purchase of 2nd share was done => Cash outflow of $120
Dividend is received => Cash Inflow of $2
Sum of these two results in cash outflow of $118 => CF1 = -$118
At T =2 : 2 shares are sold => Cash inflow of $260
Dividend is received => Cash Inflow of $3 * 2 = $6
Sum of these two results in cash inflow of $266 => CF1 = $266
Step 2: Plug the cash flow values in the financial calculator to compute the IRR (because MWR is nothing
but IRR)
IRR = 14.438% or Money Weighted Return is 14.438%
Time Weighted return Calculation:
Step 1: We should first find out the number of periods, here significant cash in-flow is happening at T=1
and cash outflow is happening at T=2. So we have one period from T=0 to T=1 and another period from
T=1 to T=2
Step 2: Compute the portfolio value just before the significant cash inflow or outflow.
For Period 1: Beginning Value = $100; Ending Value = $120; Dividend Received = $2
For Period 2: Beginning Value = $120 (for the 1st share) + $120 (amount that is invested) = $240
Ending Value = $260; Dividend Received = $6 (for 2 shares)
Note: Many candidates have confusion regarding why the beginning value of the portfolio should be
$240, why not it should be $220, the point here is that at the beginning of period 2, the first share could
be sold for $120 and there is an investment of $120 more, hence the portfolio value is $240. Also we
should consider the dividend in this period for both the shares.
Step 3: Find out the holding period return of the periods
For Period 1: HPR = (120 – 100 + 2)/100 = 22%
For Period 2: HPR = (260 – 240 + 6)/240 = 10.83%
Step 4: Find out the geometric mean return or TWR from the holding period returns
(1 + TWR)2 = (1+ HPR1)*(1+ HPR2)
=> (1 + TWR)2 = (1.22) * (1.1083) = 1.3522
=> (1 + TWR) = 1.1628 => TWR = 0.1628
Or Time Weighted return is 16.28%
Is it always the cash that Time Weighted return is less than money weighted return?
Please note that this is not the case and we got into this situation for this problem only. The next
example will clear this concept.
Concept Builder –Money Weighted Return and Time Weighted Return
6. An investor purchased one share of Goldman Sachs (GS) at $100 at T = 0, he again purchased one
more share of GS at $120 at T =1. He received total dividend of $2 at T= 1 and a dividend of $3 per share
at T =2, the investor sold the shares at T=2 for a total consideration of $360. Find money weighted and
time weighted return?
Answer
Money Weighted Return Calculation:
Step 1 : Identify the cash flows that are happening at the various intervals.
At T =0 : Purchase of 1st share was done => Cash outflow of $100 => CF0 = -$100
At T =1 : Purchase of 2nd share was done => Cash outflow of $120
Dividend is received => Cash Inflow of $2
Sum of these two results in cash outflow of $118 => CF1 = -$118
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At T =2 : 2 shares are sold => Cash inflow of $360
Dividend is received => Cash Inflow of $3 * 2 = $6
Sum of these two results in cash inflow of $366 => CF1 = $366
Step 2: Plug the cash flow values in the financial calculator to compute the IRR (because MWR is nothing
but IRR)
IRR = 41.2% or Money Weighted Return is 41.2%
Time Weighted return Calculation:
Step 1: Here significant cash in-flow is happening at T=1 and cash outflow is happening at T=2. So we
have one period from T=0 to T=1 and another period from T=1 to T=2
Step 2: Compute the portfolio value just before the significant cash inflow or outflow.
For Period 1: Beginning Value = $100; Ending Value = $120; Dividend Received = $2
For Period 2: Beginning Value = $120 (for the 1st share) + $120 (amount that is invested) = $240
Ending Value = $360; Dividend Received = $6 (for 2 shares)
Step 3: Find out the holding period return of the periods
For Period 1: HPR = (120 – 100 + 2)/100 = 22%
For Period 2: HPR = (360 – 240 + 6)/240 = 52.5%
Step 4: Find out the geometric mean return or TWR from the holding period returns
(1 + TWR)2 = (1+ HPR1)*(1+ HPR2)
=> (1 + TWR)2 = (1.22) * (1.525) = 1.8605
=> (1 + TWR) = 1.3640 => TWR = 0.364
Or Time Weighted return is 36.4%
So for this example the MWR is more than that of the TWR. So which return is more or less depends on
the amount and the timing of the cash flows.
What can we observe from the above 2 examples, either TWR or MWR can be more or less, it depends
on how the investment is done and the periodic return that is generated.
Practical Understanding of the differences in the two return measures
1. Money Weighted Return gives weightage to the money that is deposited in the account. If the
portfolio performance is good when more money is in the portfolio then the overall return
increases, where as if the portfolio performance is bad with more money the overall return
decreases.
2. In time weighted return, the return is not affected by the timing of the cash flows and the amount
of money invested, it is purely depended on the periodic return generated. For purpose of simplicity
we will assume that the holding period will be the same. In reality, for the calculation of mutual
fund returns, we define the holding period as 1 day, because typically everyday there are cash
inflows and outflows.
You need to remember the following table because many problems will not ask you to calculate the
Money weighted or Time weighted return but an understanding of the impact on the return measure
when one of these is choses.
Amount of Money compared to
previous period
Return compared to
previous period
Interpretation
More Money More Return MWR > TWR
More Money Less Return MWR < TWR
Less Money More Return MWR < TWR
Less Money Less Return MWR > TWR
© Knowledge Varsity – 2011
Important: TWR is the preferred method for return calculation in most of the investments. Only in one
case we prefer the MWR over the time weighted return and that is when the portfolio manager has the
complete control on the cash flow of the portfolio that is the portfolio manager decides on when to
increase or when to decrease the size of the portfolio.
LOS 6.e. Calculate and interpret the bank discount yield, holding period yield, effective annual yield, and
money market yield for a U.S. Treasury bill
Money market instruments are highly liquid, low risk instruments having maturity of less than 1 year.
These instruments are of two types:-
1. Discounted instruments – These instruments do not give any coupon or interest during the holding
period. These are priced at less than the face value. Face value is the amount of money that the
bondholder will receive when the bond matures. The difference between the face value and the
selling price is called as the bond discount. The investor will earn the discount value if he holds the
instrument till maturity. The best example of this type of instrument is a treasury bill.
For example a T bill having face value of $100 at maturing after 90 days will be selling now at a price
which is less than $100, let’s say the price is $99. Then $100 minus $99 or $1 is the discount.
2. Interest Bearing Instruments - These instruments will produce intermediate cash flows in the form
of interest. You can think of a money market (or income) mutual fund as an example.
Yield Measures of Treasury bill
There are various yield measures of Treasury Bills; here we will go through the formula and
understanding of each of the yield measures. You might fear that how you will remember so many
formulas, in reality there are not so many formulas; the idea is to understand the bank discount yield
really well.
1. Bank Discount Yield – Here the yield is calculated on the basis of the face value and not on the
actual investment done. The formula for bank discount yield is
Where; rBD : Bank Discount yield D: Discount of the T Bill
F: Face value of the T bill t : The time to maturity
Please note that Bank discount yield is an annualized yield, however it is not a good measure. Think
about Bank discount yield as BaD yield, the problems with it are:-
a. It is calculated on face value and not the actual price
b. The number of days in one year is treated as 360 days instead of 365 or 366
c. The calculation is based on simple interest concept rather than the compound interest
concept
2. Money market yield – This is another yield measure, here we are correcting one of the problems of
the bank discount yield, which is the return is calculated on the actual investment and not on the
face value. The formula for money market yield is given as
or
So money market yield is also not a good measure, but it is better than bank discount yield. The
problems are:-
a. The number of days in one year is treated as 360 days instead of 365 or 366
b. The calculation is based on simple interest concept rather than the compound interest
concept
3. Holding Period Yield: We have covered this concept in earlier LOS, here the yield is calculated on
the actual investment but only for the period the investment is made and it is not annualized.
For a T bill, the HPY is given as;
© Knowledge Varsity – 2011 Page 23
4. Effective Annual Yield: This is the best yield measure for the Treasury bill. It corrects the problem of
money market yield by considering
a. Compounding
b. Considering one year as 365 days
The formula is given by: -1
EAY is the annualized yield of the holding period and can be used to compare across various
investments
Based on the above, we can say that for any period
Effective Annual Yield > Money Market Yield > Bank Discount Yield
Concept Builder –Various Yield Measures
6. A T bill priced at $98 with face value of $100 and 180 days until maturity.
a. Calculate the bank discount yield
b. Find the Holding period yield
c. Find the effective annual yield
d. Find the money market yield
Answer
First calculate the discount. Discount = Face value – Price => discount = $100 - $98 = $2
a. Bank Discount Yield (The BaD Yield) = (D/F) * (360/t) = (2/100) * (360/180) = 4%
b. Holding Period Yield = D/P = 2/98 = 2.0408%
c. Effective Annual Yield = (1+ HPY)365/t – 1 => (1.020408)365/180 -1 => 1.0204082.0278 -1
=> EAY = 4.1817%
d. Money Market Yield = (D/P) * (360/t) = (2/98) * (360/180) = 4.0816%
LOS 6.f. Convert among holding period yields, money market yields, effective annual yields, and bond
equivalent yields.
There is relationship among all the yield measures, if you have understood the underlying concept of
each of the yield then you need not remember any formula.
1. Conversion from bank discount yield to Money Market yield – There is a very complex formula for
the conversion; we will not follow the formula, but the logic for this conversion.
During the conversion we will assume that the face value of the T bill is $100. The process is best
described using the below example
Concept Builder –Conversion from Bank Discount Yield to Money Market Yield
7. A T bill having 120 days to maturity is yielding 3.5% on bank discount basis, how much will be its
money market yield?
Answer
Step 1: Assume the face value to be $100, we would like to find out the discount at which the T bill is
trading
3.5 % = (D/100) * (360/120) => 3.5% = (D/100) * 3
=> D = 3.5% * 100 / 3 = $1.1667
Step 2: Once discount is calculated, Find out the price at which the bond is trading
Price = F – D => $100 - $1.667 = $98.8333
Step 3: Since now we know the discount, the price and the days to maturity, calculate MM yield
Money Market yield = (D/P) * (360/t) => (1.667/98.333) * (360/120)
=>Money Market yield = 3.5413%
2. Conversion from holding period yield to Money Market yield to Effective Annual Yield –
Please note that the
Money market yield is annualized version of HPY based on simple interest and 360 days in a year.
© Knowledge Varsity – 2011
EAY is annualized version of HPY based on compound interest and 365 days in a year.
- 1
Concept Builder –Conversion from Money Market Yield to HPY and EAY
8. A T bill having 120 days to maturity has money market yield of 3.5413%, calculate the HPY and EAY?
Answer
Holding Period Yield = 3.5413 * 120/360 = 1.1804%
EAY = (1.011804)365/120 – 1 = 3.6339%
Bond Equivalent Yield (BEY) – In US, most of the bonds pay coupon semi-annually, based on the price
of the bond, the market participants calculate the semi-annual yield of the bond. The bond equivalent
yield is based on the simple interest concept of the semi-annual yield, therefore
3. Conversion from HPY to Bond Equivalent Yield: For this conversion we first need to find the effective
semi-annual yield. Please note that when we are referring to semi-annual yield; you should convert the
semi-annual into 6 months and the holding period should also be in month. Please note that here we
need to assume compounding for the 6 months rather than simple interest. You can take 30 days as one
month period over here. We can see an example of this to understand the concept better.
Concept Builder –Conversion from HPY to BEY
9. A T bill having 120 days to maturity has HPYof 2%, calculate BEY?
Answer
First Step: Find the Holding period in months by taking 30 days as 1 month
=> holding period = 120/30 = 4 months
Second Step: Find the effective semi-annual yield
=>effective semi-annual yield = (1.02)1.5 -1 = 3.01495%
BEY = 2 * 3.01495% = 6.0299%
4. Conversion from EAY to Bond Equivalent Yield: Here the idea is to convert the EAY to effective semi-
annual yield and then find the BEY.
- 1 => BEY = 2 *{ – 1}
Concept Builder –Conversion from EAY to BEY
10. A T bill having 120 days to maturity has EAY of 5%, calculate the BEY?
Answer
First Step: Find the semi-annual yield
=> Semi-annual yield = (1.05)0.5 – 1 = 2.4695%
Second Step: Multiply the semi-annual yield by 2 to get the BEY
=> BEY = 2 * 2.4695% = 4.939%
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Concept Notes For Reading #7-Statistical Concepts and Market Returns
Reading Summary
This topic introduces the concept of descriptive statistics. The focus in this topic is on Measures of
central tendency and dispersion. You need to understand and calculate these measures. From
investment point of view, important measure of central tendency is mean and standard deviation is the
important dispersion measure. Percentiles are definitely a testable topic in the examination. A
candidate should understand the deviation of a data set from what is known as Normal distribution.
Some may find Chebysev’s inequality to be a difficult concept, but an understanding of it would make
life easier in Readings 10 and 11. Problems related to Skewness and Kurtosis are favorites of the
Institute. Sharpe Ratio is a concept which is found in portfolio management also.
LOS 7.a.Differentiate between descriptive statistics and inferential statistics, between a population and a sample, and among the types of measurement scales;
Statistics can be used to refer to numerical data (as an example the net profit of a firm over the last 10
years). It can also be used to refer to the methods of collecting, classifying, interpreting or analyzing the
data. Statistics are widely used in finance and its applications should be well understood by the finance
professionals.
Following are the two categories of statistics:-
Descriptive Statistics –This is the branch of statistics where we describe the important aspects or
characteristics of the data set that have been collected. The description can consists of
o Measure of Central Tendency -Where the data is centered, like mean
o Measure of dispersion - How the data is spread out, like range
In this reading we will focus on the descriptive statistics, we would understand the concepts
through which we can describe huge amount of data sets, thus trying to make sense of the data.
Inferential Statistics –This branch of statistics deals with prediction or inference of the large set of
data (population) from small set of data (a sample). As an example suppose we want to know the
average height of the men aged between 20 and 25, then it would be impossible to measure the
height of each and every man. What we can do is to take a sample of the men across the various
cities/town/villages and then find out the average. Using this simple average we can try to estimate
the average height of the men population. Please note that since we are trying to predict, there will
always be an error associated with the prediction. We will focus on this part of statistics in Reading
10 and Reading 11.
We have used the word population and sample in the paragraphs above; let’s see what is meant by
these terms
Population –A population can be thought of as a universal set. It consists of the entire data set or
has each and every member of the specified group. As an example, all the men of India aged
between 20 and 25 would form a population. An important point to note is that the population
doesn’t have anything to do with the human. We can have a population of living, non-living or even
virtual objects.
Sample – A sample is a subset of the population or in other words we can say that a sample
contains some of the member of the population. It is impractical to conduct analysis on a
population and hence typically we select a sample from the population. The best is to get a random
sample from the population but sometimes we may be interested in something more specific. We
will cover Sampling later in Reading 10.
© Knowledge Varsity – 2011
Measurement Scales
When dealing with data, it becomes important to organize the data. The ways in which data can be
organized are listed below
Nominal (Grouping): This is the weakest level of measurement scale. Here we only categorize or
group the data. However in no way we would be able to find out which group of data is better as
there is no ranking done.
Example of Nominal Scale would be categorizing the stocks in Large Cap; Small Cap etc.
• Ordinal(Grouping and Ranking): This is better measurement than the nominal scale. In this scale
the data is grouped as well as ranked. In Ordinal scale the data is ordered data (or ranked data)
which means assigning some rating or value to a group with a view that one group is better than the
other based on the value. However it provides no information on differences in performance
between groups.
Example: Categorizing the stocks based on performance; like assigning 5 star rating to the top 20%
stocks. Another example is of bond rating, where the bonds are rated as AAA, AA, A etc., a bond
with a rating of AAA will be safer than that of a bond with rating of AA, but we don’t have
information on how much better the AAA bond is as compared to AA bond.
• Interval(Grouping, Ranking, includes exact distance): This scale is one step further, here we work
with ranked data but we make sure that the difference between scale values are equal. Here the
values can be added or subtracted. However a value of zero here does not mean the absence of
what is being measured, in simpler words this scale lacks “True Zero”. We will try to explain this
concept using the below two examples
Example 1:Temperature is measured in Celsius scale which is an interval scale. Water freezes at a
temperature of 0 but Zero 0Cdoes not mean absence of temperature because we have temperature
value in negative also. In reality the true absence of temperature is observed at -273 0C which is also
Zero Kelvin. Now in the absence of true zero, we can’t say that 50 0C is twice that of 25 0C, so a
meaningful comparison is not possible in this scale.
Example 2:In GMAT examination, it is not possible for a candidate to score zero marks. The
candidates are assigned marks in multiples of 10. So a person scoring 800 in GMAT has not score
two times that person who has scored 400 in GMAT.
• Ratio: Ratio scale is the strongest measurement scale, it has all the qualities of interval scale plus it
also provides a true zero. Since we have a true zero, meaningful comparison can be made among
values. This is the most important scale, here the datasets can be evaluated on the basis of ratio.
Example 1: The amount of money a person has can be considered as Ratio scale, a person having
$10,000 has twice as much money as a person having $5,000.
Example 2: In a typical traditional examination, having 100 marks, a person can score zero marks
also, here we can say that a person scoring 100 marks has scored 2 times of a person scoring 50
marks.
Note: For remembering the measurement scale you can remember NOIR (meaning black in French).
Concept Builder – Identification of the scales
1. In the cases given below, identify what type of scale it represents
A. Ranking of mutual funds by Morning Star
B. Runs scored by a player in a cricket match
C. Measurement of temperature in Fahrenheit scale
D. Classification of students in a class on the basis of sex
Explanation
A. Morning Star, assigns a one star to five star ranking. Five star ranking is given to the best funds
as determined by Morning Star’s evaluation criterion. Here we can say that a 5 star mutual fund
© Knowledge Varsity – 2011 Page 27
is better than a 2 star mutual fund, but we can’t say by exactly how much, hence it is an
example of ordinal scale.
B. The run scored can’t be negative. A batsman who scores 100 runs has scored twice as much a
batsman who has scored 50 runs. Hence, it is an example of Ratio Scale.
C. Fahrenheit scale like Celsius scale doesn’t have a true zero, but we can identify the difference
between the temperatures and hence it is a measure of interval scale.
D. Classification on the basis of sex into male or female is just grouping and hence it is an example
of Nominal Scale.
LOS 7.b. Define a parameter, a sample statistic, and a frequency distribution
Parameter – A parameter is a numerical quantity measuring some characteristics of the population. In
statistics we have to deal with many parameters, but from our point of view, we are mainly interested
in mean standard deviation of the returns. Parameters are usually denoted by Greek letters. For
example, population mean is denoted by µ (pronounced as mu) and population standard deviation is
denoted by σ (called as sigma).
Sample Statistics – A sample statistics is a numerical quantity measuring the characteristics of the
sample. A sample mean is denoted by , whereas sample standard deviation is denoted by s. As
mentioned earlier, most of the times population parameters are not known and they have to be
estimated from sample, so we find out sample statistics to make prediction of the population
parameter.
Mostly we deal with large data sets and it becomes difficult to deal with individual member of the set,
frequency distribution is a simpler way of dealing with the data.
The process of creation of Frequency distribution is outlined in the following steps
Step 1 - We first create an interval (also known as class), which is basically a group. Following
points are important
A. An observation has to fall in one of the interval.
B. The intervals should not overlap (that is they are mutually exclusive)
C. Also an interval has a lower limit and an upper limit.
Please note that an interval need not be a range always, it can be classified as one of the scale
measure. For example we can have a Class as
1. Just grouping (Nominal) – Type of bond, Govt., private etc.
2. Ranking (Ordinal) - AAA bonds, AA bonds etc.
3. Interval scale – Have a range of return from these bonds
4. Ratio Scale – Have the bond grouped as per the coupon rate
Step 2 –Assign the observation in the data set to the class that you have identified in Step 1.This
process is called as tallying the data.
Step 3 – Count the number of observation in each of the class, this number is called as the class
frequency or frequency or absolute frequency.
Note: Please note that in the examination, you will NOT be asked to construct a frequency distribution
table, the example below is an illustration of the process. However there can be a question (very low
probability) where you would be asked to find the frequency of a class interval.
© Knowledge Varsity – 2011
Concept Builder – Frequency Distribution
2. Given the following returns data for a stock in the month of January 20X1, construct a frequency
distribution table
-3.60 3.23 5.32 -5.84 -17.99
-7.14 2.26 6.42 6.70 17.51
-9.26 7.89 0.89 -2.85 -10.50
3.17 -3.25 2.09 -13.98 6.23
3.87 -6.70 1.20 -18.22 18.57 Explanation
For each observation, identify which class interval it should belong to and draw a line in the Tally
column. Once done, count the number to identify the absolute frequency.
Class Interval Tally Absolute Frequency
-20% ≤ R < 15% // 2
-15% ≤ R < 10% // 2
-10% ≤ R < 5% /// 3
-5% ≤ R < 0% //// 4
0% ≤ R < 5% //// // 7
5% ≤ R < 10% //// 5
10% ≤ R < 15% 0
15% ≤ R < 20% // 2
Total 25
LOS 7.c. Calculate and interpret relative frequencies and cumulative relative frequencies, given a frequency distribution
Lets now define the following types of frequency that we observe in a frequency distribution
Absolute Frequency – This is the actual number of frequency of a given interval. The minimum
value of absolute frequency is ZERO, It can’t be negative.
Relative Frequency –This measures how much time one of the class has occurred as relative to
the entire class. Numerically,
Cumulative Absolute Frequency and Cumulative Relative Frequency – Starting from the first
class and moving down the classes, we can add the absolute and relative frequencies to get the
cumulative absolute and cumulative relative frequency. Since the frequency will always be
greater than or equal to ZERO, the cumulative frequencies are always increasing or remaining
the same.
The below example will build upon the example #2 to explain the concepts of this LOS.
© Knowledge Varsity – 2011 Page 29
Concept Builder – Relative and Cumulative Frequencies
3. Given the following returns data for a stock in the month of January 20X1, construct a frequency
distribution table
Explanation
We will use the formula given in the text above to calculate each of the measure.
Class Interval Absolute
Frequency Relative
Frequency
Cumulative Absolute
Frequency
Cumulative Relative
Frequency
-20% ≤ R < 15% 2 0.08 2 0.08
-15% ≤ R < 10% 2 0.08 4 0.16
-10% ≤ R < 5% 3 0.12 7 0.28
-5% ≤ R < 0% 4 0.16 11 0.44
0% ≤ R < 5% 7 0.28 18 0.72
5% ≤ R < 10% 5 0.2 23 0.92
10% ≤ R < 15% 0 0 23 0.92
15% ≤ R < 20% 2 0.08 25 1
Total 25 1
LOS 7.d. describe the properties of a data set presented as a histogram or a frequency polygon
Histogram – It is a bar chart (without space between the bars) that is constructed using the frequency
distribution. On the X (horizontal) Axis we plot the Class and on the Y Axis (Vertical Axis) we plot the
frequency. Looking at the histogram, you can easily identify some distribution characteristic, that is
which class has the highest, lowest frequency, how the data is dispersed etc. Hence histogram is a very
useful tool for an analyst.
Frequency Polygon – This is a similar representation like the histogram, but here we don’t display the
bars. The mid-points of the intervals are joined with a line to create a polygon structure.
© Knowledge Varsity – 2011
LOS 7.e. define, calculate, and interpret measures of central tendency, including the population mean, sample mean, arithmetic mean, weighted average or mean (including a portfolio return viewed as a weighted mean), geometric mean,harmonic mean, median, and mode
Measures of Central Tendency - Central tendency refers to the presence of center in a data set. There
are various measures through which we try to identify the central (or middle) point of a population or a
sample. Please note that practically it is expensive to find out the central tendency measures for a
population.
Population Mean is the average value of a population, there is only one mean for one population. The
formula for a population mean is given as
Where are the individual members or data point of a population. N is the population size (that is the
number of data point in the population).
Sample Mean is the average value of a sample, there is only one mean foronesample. But from a
population we can create many samples; hence we can have many sample means for one population.
We compute sample mean and estimate the population mean from the sample means.
The formula for a population mean is given as
Note that we are using N (big) to denote the population size and n (small) to denote the sample size.
Arithmetic Mean is the simple average for any data set. The population and the sample mean which we
have explained above fall in the category of the arithmetic mean. Arithmetic mean is the most popular
measure of central tendency because of its calculation simplicity.
Properties of Arithmetic Mean:
1. Arithmetic mean is unique
2. Arithmetic mean is only applicable to interval and ratio scale. Arithmetic mean is meaningless for
nominal and ordinal scale.
3. Needless to say that arithmetic mean can only be computed by taking the sum of all the data points
in the set, its value will be inaccurate if you exclude some data purposely.
4. Sum of the deviations from the mean is ZERO. First let’s define what deviation is – A deviation is the
distance between the mean and one data point.
Concept Builder – Deviation from the Mean
4. As an example consider the following data set - 10, 20, 25, 5
The mean of this data set is (10+20+25+5)/4 = 15. Please note that there is no data point which has
value of 15, so it’s not necessary that mean would be equal to one of the data point.
Now let’s find the deviation:
Data Point Mean Deviation
10 15 (10-15) = -5
20 15 (20-15) =5
25 15 (25-15) = 10
5 15 (5 -15) = -10
Sum Of Deviation -5 + 5 + 10 + -10 = 0
Deviation is important information for a data set, as it is a measure of risk. We will cover this point
when we are covering the dispersion topic.
Advantages of Arithmetic Mean:
1. Easy to calculate
2. Mean uses all the information about the size and magnitude of the observation (or data points)
Disadvantages of Arithmetic Mean:
© Knowledge Varsity – 2011 Page 31
1. Mean is highly sensitive to the extreme values, a higher value will be able to attract the mean
towards its side. For example in MBA colleges, average salary is not a good measure because some
students get very high salary and as a result, the mean is high. For the following data set - 10, 20, 25,
965, the mean is 250. See the impact on the mean because of the presence of a high number (as
compared to the previous example). In such cases median is a better measure.
2. Mean cannot be calculated for a data set which is not finite, that is the number of data points is not
known.
Median: Median divides a data set into two equal parts; it means that median is the Mid-Point of a
sorted data set. The data set can be sorted either in ascending or descending order.
For an odd number of data set, median is easier to identify as we have a data point which is the middle
value. For odd number, the median is {(n+1)/2}th data point
Concept Builder – Calculation of median for odd number of observation
5. A stock has generated the following returns over the past 5 days
-2%, 5%, 4%, 2%, 8%
Compute the median of the stock return?
Explanation
For computing the median, first we need to arrange the data in either ascending or descending order.
Lets arrange in ascending order
-2%, 2%, 4%, 5%, 8%
There are total of 5 data points, since this is an odd number the median will be {(5+1)/2}th number or
(6/2)th or 3rd number.
The 3rd number here is 4%. Hence the median is 4%.
For an even number of data set, the median needs to be calculated. Median is the average of the
(n/2)th and ((n/2) + 1)th data point (or observation)
Concept Builder – Calculation of median for odd number of observation
6. A stock has generated the following returns over the past 4 days
-2%, 5%, 4%, 2%
Compute the median of the stock return?
Explanation
For computing the median, first we need to arrange the data in either ascending or descending order.
Lets arrange in ascending order
-2%, 2%, 4%, 5%
There are total of 4 data points, since this is an even number the median will be the average of the
(4/)2th and {(4/2)+1}th number or Average of 2nd and 3rd number.
2nd Number is 2%, 3rd number is 4%. Hence the average is (2% + 4%)/2 = 3%
Hence the median is 3%.
Mode: The mode is the most frequently occurring data point (or observation) in a data set (population
or a sample).
Unlike Mean and Median, It is not necessary that a data set should have a mode. If all the observation in
a data set is different, then it is said to have No Mode.
Unimodal – When a data set has only one observation which has the highest frequency (or most
occurrences) then the data set is said to have One Mode (or Unimodal)
Bimodal -When a data set has only two observations having the highest frequency (or most
occurrences) then the data set is said to have Two mode (or Bimodal)
© Knowledge Varsity – 2011
Modal Interval – In a frequency distribution with class intervals, we can’t classify as single data point
and hence finding mode is not possible, However, we can find out the class interval which has the
highest frequency, that class interval is said to be the modal interval.
Concept Builder – Mode
7. Find the mode for the following data set.
a. 5%, 7%, 9%, 11%, 13%
b. 5%, 7%, 9%, 5%, 11%, 13%,
c. 5%, 7%, 9%, 5%, 11%, 13%,13%
Explanation
a. There is no observation which is occurring more than once, and hence no mode exist for
this data set
b. The observation 5% is coming twice in the data set, and hence the mode is 5%
c. The observations 5% and 13% are coming twice in the data set, so this is an example of
bimodal distribution
Other Concepts of Mean
Earlier we have covered arithmetic mean which is an important concept, but in investment we use
other concepts of mean also, and it’s worthwhile to cover those concepts.
The Weighted Mean The concept of weighted mean is used in portfolio analysis. The idea behind weighted mean is that not all observation has the same weight and hence if we take a simple average, then the resulting answer would not be accurate. Before moving to this concept, let’s see the example given below
Concept Builder – Why We Need Weighted Mean
8. Consider that you have made investment in 3 stocks at T=0 and after one year (i.e. at T=1) you sell
the stock. You would want to know the return that has been generated. The purchase price (at T=0)
and the price at T=1 (the price at which you sold the stock) is given in the table below. Assuming
that you have purchased one share of each stock.
Stock Price at T=0 Price at T=1 Return
A $100 $120 20%
B $60 $66 10%
C $40 $80 100%
What should be the return as per your understanding, Should it be the arithmetic mean of the return?
Let’s compute the arithmetic mean
It would be equal to (20%+10%+100%)/3 = 43.33%
Now, let’s think in term of the money that is invested at T=0 and the money that you got when you sold
the stocks at T=1.
Money Invested = $100 + $60 + $40 = $200
Money Received from selling the stocks = $120 + $66 + $80 = $266
So the return that you generated = ($266 - $200)/$200 = 33%
Now, compare the return that your portfolio has generated with the arithmetic mean return, they are
not same. Hence there should be a way in which we should be able to find out the mean return.
Weighted mean is the concept through which we would be able to find out that.
In weighted mean calculation, we assign a weight to each observation. For stocks in the portfolio, the
weight is the amount of money invested in them.
© Knowledge Varsity – 2011 Page 33
Where, X1 , X2 , …. Xn are the observations
W1 , W2 , …. Wn are the weights assigned to these observations
Please note that, it is must to have the sum of the weights equal to 1, that is
In case of a portfolio of stocks, the Weight is given as
Now let’s solve the example above using the weighted mean formula, we should be getting the same
answer
Concept Builder –Weighted Mean
9. Consider that you have made investment in 3 stocks at T=0 and after one year (i.e. at T=1) you sell
the stock. You would want to know the return that has been generated. The purchase price (at T=0)
and the price at T=1 (the price at which you sold the stock) is given in the table below. Assuming
that you have purchased one share of each stock.
Stock Price at T=0 Price at T=1 Return
A $100 $120 20%
B $60 $66 10%
C $40 $80 100%
Explanation
First We need to calculate the weight of each of the stocks in the portfolio
WA = Amount invested in A / Total amount invested => $100/$200 = 0.5
WB = $60/$200 = 0.3
WC = $40/$200 = 0.2
Please check that the sum of the weight is equal to 1 => 0.5+0.3+0.2 = 1
Now, apply the weighted mean formula on the returns that we are seeing
Weighted Mean Return = WA RA+ WB RB+ Wc Rc = 0.5*20% + 0.3 * 10% + 0.2 * 100% = 10% + 3% + 20%
Weighted Mean Return =33%
This is the same return which we got in the previous example.
Hence, for portfolio return, weighted mean is the appropriate return measure.
The Geometric Mean
Geometric mean is used to calculate investment returns over multiple time periods. It is also used to
compute the average growth rate over a period, for example, the average sales growth of a firm over
last 5 years. When calculating the average growth rate it is called as Compounded Annual Growth Rate
of CAGR.
The formula for Geometric mean is given below
Given that Xi ≥ 0 for i=1 , 2, 3 …… n
Where, GM is the Geometric Mean.
X1 ,X2,…… Xn are the observation and n is total number of observation
However this formula can’t be used to calculate the Geometric mean of the returns, because the
returns can be negative and we can’t have negative number inside the root.
So, a solution for that is to replace each Xi with (1 + Return in decimal form). Now for any traditional
investment the return will not be less than -100% (that is you can’t lose more than what you have
invested), so we will not have any negative value inside the root.
So, for returns the Geometric Mean is given by the following formula
© Knowledge Varsity – 2011
Where, RG is the Geometric Mean.
R1 ,R2,…… Rn are the returns and n is total number of returns
Concept Builder –Geometric Mean Return
10. Consider that you have made investment in a stock at T=0, it provided a return of 10% in the first
year, 20% in the second year and -30% in the third year. How much is the return you have received
from the stock over the past 3 years?
Explanation
R1 = 10% or 0.1; R2 = 0.2; R3 = -0.3
(1+R1) = 1.1 ; (1+R2) = 1.2 and (1+R3) = 0.7
(1+ RG) = => (1+RG) = => (1+ RG) = 0.974
RG = -0.026 or -2.6%
So, this geometric mean return means that you have lost your money at a rate of 2.6% every
year.
And if you had invested $100 at T=0, it would have become $92.4 (Think How!!)
This is the most appropriate place to cover the last LOS of this reading. The LOS is given below
LOS 7.l. Discuss the use of arithmetic mean or geometric mean when determining investment returns
Now to calculate the performance of any portfolio over a time period, should we use Arithmetic Mean
return or Geometric Mean Return?
Let’s take an example to explain this scenario.
Concept Builder –Geometric Mean Return Versus Arithmetic Mean Return
11. Consider that you have made investment in a stock and it provided a return of 100% in the first year
and -50% in the second year. How much is the return you have received from the stock?
Explanation
Rather than getting into complication, let’s work from basic reasoning. Let’s assume that you had
invested $100 in the stock at T=0.
Since the first year return is 100%, the value of your stock will be $200 at T=1.
Now, in the 2nd year, the return is -50%, therefore the value of your stock will be $100 at T=2.
So, you started with $100 and have $100 in the end.
It implies that over the 2 years, the return is 0%, so it means that the average return should also be 0%.
Suppose, we use Arithmetic Mean return to explain the return over the 2 year period. The arithmetic
mean return will be (100% + -50%)/2 = 25%
But, we see that the return is 0% over the 2 years. This implies that the Arithmetic mean return is not a
correct measure to find the average stock return.
Now Let’s calculate the Geometric mean return over the 2 years.
R1 = 100% or 1; R2 = -0.5
(1+R1) = 2and (1+R2) = 0.5
(1+ RG) = => (1+RG) = => (1+ RG) = 1
RG = 0 or 0%
So, the geometric mean return is 0%, which is the actual average return that we have calculated.
So, from the above example it is clear that the Geometric Mean return is the correct measure of the
average return over a period of Time.
© Knowledge Varsity – 2011 Page 35
The Harmonic Mean
As compared to the arithmetic and geometric mean, harmonic mean is used lesser in the investment
industry. One scenario, where harmonic mean is used is to find out the average purchase price of shares
when somebody is depositing equal dollar amount in the stock every period. BTW when somebody is
depositing equal amount every month or every period, the concept is called as Dollar Cost Averaging
and in India, we also know this by the term Systematic Investment Plan.
Let’s first try to find out the average purchase price of the stock when dollar cost averaging scheme is
adopted and in the process we will derive the formula of the harmonic mean.
Concept Builder –Harmonic Mean Return
12. Suppose you as an investor have invested in a Systematic Investment Plan of HDFC Tax Saver Fund.
You are making contribution of $1000 every month in the fund. The below table outlines the price
of the fund at which you have made the investment. What is the average purchase price at which
you bought the fund?
Note: You will learn in the later chapters that for Mutual funds, the price at which we buy is not
called as price but it is known as NAV (Net Asset Value)
Time Investment Price (NAV)
T=0 $1000 $100
T=1 $1000 $125
T=2 $1000 $80
Explanation
Will the answer be the arithmetic mean of the price for the 3 periods?
Let’s find the arithmetic mean, which will be ($100+$125+$80) = $305/3 = $101.67
Let’s try to build the following table, where we identify the number of units of the mutual fund that we
have bought.
Time Investment Price (NAV) Number of Units
T=0 $1000 $100 =$1000/$100 = 10
T=1 $1000 $125 =$1000/$125 = 8
T=2 $1000 $80 =$1000/$80 = 12.5
So, the total investment is 3 * $1000 = $3000
Total Number of units that is bought is 10 + 8 + 12.5 = 30.5
We know that logically, the average purchase price should be equal to total investment divided by the
total number of units
Average price = $3000 / 30.5 = $98.3606
So, it implies that the arithmetic mean is not the correct approach to find out the average purchase
price in Dollar Cost Averaging method.
Now, what exactly we have calculated which we are saying as the correct answer?
We have calculated the harmonic mean of the purchase price, and that is the correct mean.
Let’s try to rewrite the Average Price Equation, which we have in the above
Now, $1000 will get cancelled in the numerator and the denominator
Or,
This is the formula of the Harmonic Mean, which is given in detail in the text below
© Knowledge Varsity – 2011
Harmonic mean for a set of observation X1 ,X2 …… Xnis given by the following formula
Or in more general format
LOS 7.f. Describe, calculate, and interpret quartiles, quintiles, deciles, and percentiles
Other Measures of Location – Quantiles
Median divides a distribution into half. The concept of Quantile divides the distribution into smaller
sizes. Median and quantiles are known as measure of location. Following are the examples of Quantiles
Percentiles – The distribution is divided into 100 parts.
Deciles – The distribution is divided into 10 parts. (Think Deca)
Quintiles – The distribution is divided into 5 parts.
Quartiles – The distribution is divided into 4 parts. (Think Quarter)
Any quantile can be expressed as a percentile. So we use a standard formula to represent the quantiles.
As an example, 3rd quintile (or 3/5th) is same as 60 percentile. This is because when we mention 3rd
quintile, it means that 60% of the data are below the particular value or observation.
For a data set having n members and arranged in ascending order, the formula for finding out the
position for a given percentile y is
Here Ly is the position that we will get in the sorted data set.
Y is the given percentile.
So, if we are asked to find out the 2nd quartile, then y will be 50. If we are asked to find 6thdecile then y
will be 60. If we are asked to find out 90 percentile then y will be 90.
Also note that when we are calculating using the formula, we are essentially finding out the position (or
level) at which y percent of the data set will be below that particular position.
100 percentile means that 100% of the data is below the particular observation, which is not possible.
Hence the formula has (n+1) in it.
Concept Builder –Quantiles
13. Suppose there are 9 stocks in a portfolio, whose returns are given below. Find out the 4th quintile
of the stock returns.
-5%, 4%, 3%, 10%, 2%, 8%, -10%, 7% and 12%
Explanation
First arrange the returns in ascending order
-10%, -5%, 2%, 3%, 4%, 7%, 8%, 10%, 12%
Now we need to find the position at which we will get the 4th quintile.
4th quintile is same as 80 percentile.
=> Ly = 8
Therefore, the 4th quintile is 8th data from the left.
The 8th data is 10%, and hence the 4th quintile is 10%. Or we can say that 80% of the distribution is
below 10%.
Now, let’s see what happens when we do not get a whole number as the position. Whenever this
happens, we need to apply interpolation to get the value. This is a very simple concept related to
unitary method, it would be clear from the following example.
© Knowledge Varsity – 2011 Page 37
Concept Builder – Quantiles
14. Suppose you have added one more stock in the portfolio and now there are 10 stocks in the
portfolio, whose returns are given below. Find out the 4th quintile of the stock returns.
-5%, 4%, 3%, 10%, 2%, 8%, -10%, 7% , 12% and 18%
Explanation
First arrange the returns in ascending order
-10%, -5%, 2%, 3%, 4%, 7%, 8%, 10%, 12%, 18%
Now we need to find the position at which we will get the 4th quintile.
4th quintile is same as 80 percentile.
=> Ly = 8.8
Therefore, the 4th quintile is 8.8th data from the left. Now 9th data is 12% and 8th data is 10%, this
means that the value would be between 10% and 12%. What we can say is that the value will be 10% +
0.8 times the difference between 12% and 10%.
This is because for 1 unit, the difference is 12% minus 10% or 2%, therefore for 0.8 units, the difference
will be 0.8 times 2%, this concept is Interpolation.
So the value will be = 8th Value + 0.8 * (9th Value – 8th Value)
10% + 0.8 * (12% - 10%) => 10% + 0.8* 2% = 11.6%
So the 4th quintile is 11.6%, so we can say that 80% of the distribution is below 11.6%
IMPORTANT: We will apply interpolation only when the data set is population. When the data set is a
sample, then interpolation should not be used. So, if we had mentioned that in this example, it was a
sample then the interpolation would not have been used. The Ly value was 8.8, so we would just take
the integer part of it, which in this case is 8, so the value would be the observation in the 8th position.
Hence it would still be 10%.
LOS 7.g. Define, calculate, and interpret 1) a range and a mean absolute deviation and 2) the variance
and standard deviation of a population and of a sample
Measures of Dispersion
This LOS covers the measures of dispersion, that is, how the data is dispersed around the central
tendency or simply mean. We can think of mean as the reward for investing and dispersion as the risk
associated with investing.
There are two types of dispersion
Absolute Dispersion – Absolute dispersion is the amount of variability present in a distribution
without considering any benchmark or any reference point. In this LOS we will discuss about
Absolute dispersion. The measures of absolute dispersion are range, mean absolute deviation,
variance and standard deviation.
Relative Dispersion - Relative dispersion isthe amount of variability present in a distribution relative
to a benchmark or a reference value. Coefficient of variation is an example of relative dispersion
and is covered in LOS i.
Range is the simplest measure of dispersion. Here we are just interested in finding out the distance
between the maximum and the minimum value in a distribution. It is useful when we are comparing
two data set (or distribution) and it is very simple to compute.
Range has the following disadvantages
It uses only two values from the distribution
It is very sensitive to the extreme values.
Does not give any idea about the shape of the distribution
As a result, range is not used on a stand-alone basis but is used to supplement other measures of
dispersion.
© Knowledge Varsity – 2011
Mean Absolute Deviation – While covering arithmetic mean, we calculated the mean deviation and we
found that it was always ZERO. Using the deviation we can get information about the dispersion but we
need to address the problem of the sum coming zero, a solution is to take only the absolute value of the
deviation, that is, when the deviation is negative, we ignore the negative sign and take the value. Hence
Mean absolute deviation is the average of the absolute deviation around the mean. The formula is
Here is the sample mean, is the observation and n is the total number of observations.
MAD is a better measure than the range, but mathematically it has been found that it’s not the most
superior measure of dispersion and hence we move on to the next measure which is Variance.
Variance – In MAD, we had taken absolute measure to get the positive deviation. Another way to get
positive deviation is to square the deviations. Mathematically this is a better measure. By taking the
average of the squared deviations we get Variance. There are differences in the variance calculation
when we are calculating for population and when it is calculated for sample. The formula for Population
Variance is given below
Here, is the population mean and is the size of the population
Sample Variance –Statistically, it has been found that if we use the population variance formula to find
out the sample variance, the variance thus obtained was lesser than what is actually observed for a
sample. To remove this bias, it has been suggested to divide the squared deviations by (n-1) rather than
n. The sample variance thus obtained was closer to what was actually observed. The formula for sample
variance is given below
Here, is the sample mean and n is the size of the sample
Standard Deviation - Variance is the best measure for dispersion, however if you observe, variance is a
squared number and hence its unit is also squared. For example if we are measuring the variance of
height of a group of people, the unit of variance will be height squared. We as human would like to
think in linear measures and also all the calculation that we perform on the distributions are linear and
hence it became important to have a measure which is linear along with a superior measure of
dispersion. The solution is to take the square root of the variance. The value obtained after taking the
root is known as standard deviation. So, variance is essentially square of the standard deviation.
The population standard deviation is denoted by σ (called as sigma), therefore the population variance
is denoted by σ2. So, the formula for population standard deviation will be
The sample standard deviation is denoted by s, therefore the sample variance is denoted by s2. The
formula for sample standard deviation is given as
© Knowledge Varsity – 2011 Page 39
Concept Builder – Measures of Dispersion
15. A stock has the following returns over the past 7 years
7%, 6%, 9%, 10%,11%,2%, 4%
You are interested in finding out the measures of dispersion.
a. What is the range?
b. What is the Mean Absolute Deviation (MAD)?
c. What is the sample and population variance?
d. What is the sample and population standard deviation?
Explanation
Range : Range is the difference between the highest and the lowest return values
Range = 11% - 2% = 9%
MAD: Before we find MAD, we will have to find the mean of the returns
Mean = (7+6+9+10+11+2+4)/7 = 7%
MAD = 2.57%
For the rest of the calculations, it is better to use the financial calculator.
Using our TI BA II Plus Financial Calculator, we can easily find the variance and the deviation.
Press 2nd ; Press 7 ; It means you are pressing DATA.
Press 2nd Press CE|C ; It means you are pressing Clear Work
You will find in your calculator X01 , the calculator is asking you to input the value here.
Please note that since we have only one set of data, we will work with only the X data series.
Now Press 7 and then Press ENTER. You will see a down arrow, you will have to Press it Twice ↓↓
You will get X02, press 6 and then Press ENTER, again press ↓↓.
The below has the subsequent steps that you need to perform
Press 9 Press ENTER Press ↓↓
Press 10 Press ENTER Press ↓↓
Press 11 Press ENTER Press ↓↓
Press 2 Press ENTER Press ↓↓
Press 4 ENTER
So, you have entered total of 7 data.
Now we need to go to the Statistics function in the calculator
Press 2nd ; Press 8, it means that you are pressing STAT.
You will see LIN in the display, it means that you are working on linear data.
Now Press ↓=> You will see n = 7, double check that your total data points were 7
Now Press ↓=> You will see , = 7, which is the mean of the data (we calculated the same earlier)
Now Press ↓=> You will see ,Sx = 3.26598, which is the sample standard deviation
Now Press ↓=> You will see , σx = 3.023716, which is the population standard deviation
For this exercise, these were the only calculation that you had to perform in the calculator
Population Variance can be found out by squaring the population standard deviation.
Population Variance = 9.14%2
Sample Variance can be found out by squaring the sample standard deviation.
Sample Variance = 10.67%2
Before moving to other LOS, we will visit LOS i as it is closely tied with the concepts which we have
discussed in this LOS.
© Knowledge Varsity – 2011
LOS 7.i. Define, calculate, and interpret the coefficient of variation and the Sharpe ratio
When we are comparing two distributions which have large differences in the mean and the variance, it
becomes difficult to compare with the absolute dispersion measure, In such cases we employ relative
dispersion measure.
Coefficient of Variation (CV) is a relative dispersion measure and is used to standardize the absolute
dispersion measure. It is given by the following formula
For portfolios, CV measures the amount of Risk (deviation) per unit of return of the portfolio. We would
like to have lesser risk per unit of return and hence the lower the coefficient of variation, the better it
is.
Concept Builder – Coefficient Of Variation
16. You are Fund Of Fund Investment manager and would like to invest some money in one of the fund.
You are evaluating two fund managers and would like to invest in one of them. The following table
has the return and the standard deviation data for the two fund managers. Based on the concept of
Coefficient of Variation, with which fund manager would you invest and why?
Fund Manager Return Standard Deviation (Risk)
A 10% 20%
B 15% 25%
Explanation
You might think it is better to invest with A because he has lower variability of the return. But note that
here we are seeing that the funds have different return and risk measure, and hence we are unable to
make a decision based on the absolute measure. We will have to employ a relative measure to find out
the best manager.
Coefficient of Variation (CV) which measures the risk per unit of return would be ideal here. So we will
compute the CV for both the manager. Computation is shown below
Fund Manager Return Standard Deviation (Risk) CV
A 10% 20% =20/10 = 2
B 15% 25% = 25/15 = 1.67
Since the fund manager B has lower Coefficient of Variation (risk per unit of return) we should invest in
B’s fund.
Sharpe Ratio – This ratio is attributed to Prof. William Sharpe and he received Nobel Prize for coming up
with this concept. This ratio is basically a reward to risk ratio and has prominent place in the
investment industry. Using this ratio we are able to compare the portfolios on risk and return
characteristics. You may find it similar to the coefficient of variation, but this ratio is far more reaching
that coefficient of variation because it measures the excess return over the risk free rate. The idea on
which it is built is that, Since there is no risk when one invest in risk free asset, one should not look at
the absolute return from any investment but should look at the excess return that the investment is
generating over the risk free rate and then compare investments on the excess return versus the risk.
Sharpe ratio is opposite to the coefficient of variation, here we measure the excess return generated
per unit of risk taken. It would become clearer from its formula
Here, is the portfolio return, RFR is the risk free rate of return, is the standard deviation (or risk)
of the portfolio.
Since higher excess return per unit of risk is better, hence higher the Sharpe ratio, the better it is.
© Knowledge Varsity – 2011 Page 41
Concept Builder –Sharpe Ratio
17. The data is same as that of the previous problem. Additionally risk free rate of return is given as 4%.
Based on Sharpe Ratio, with which fund manager would you invest and why?
Explanation
The following table has the calculation of Sharpe Ratio in the fourth column.
Fund Manager Return Standard Deviation (Risk) Sharpe Ratio
A 10% 20% =(10-4)/20 = 0.3
B 15% 25% = (15-4)/25 = 0.44
Since the fund manager B has higher Sharpe Ratio (excess return per unit of risk) than fund manager A,
we should invest in B’s fund.
IMPORTANT: Compare, this example with the previous example, in both the case we have got the same
answer, which is to invest in B’s fund. Is it always the case that the result in which portfolio to invest is
same in Sharpe Ratio and Coefficient of Variation?
The example, here are peculiar and it is by chance that we are getting the same return, It is not always
the case. Let’s see the next example.
Concept Builder – Coefficient of Variation Versus Sharpe Ratio
18. You are Fund Of Fund Investment manager and would like to invest some money in one of the fund.
You are evaluating two fund managers and would like to invest in one of them. The following table
has the return and the standard deviation data for the two fund managers. The risk free rate of
return is 7%. Based on the concept of Coefficient of Variation and Sharpe Ratio, find out with which
fund manager would you invest and why?
Fund Manager Return Standard Deviation (Risk)
A 12% 15%
B 14% 20%
Explanation
The following table has the calculation of CV and the Sharpe Ratio.
Fund Manager Return Standard Deviation CV Sharpe Ratio
A 12% 15% =15/12 = 1.25 =(12-7)/15 = 0.33
B 14% 20% = 20/14 = 1.43 = (14-7)/20 = 0.35
As per the CV, Fund manager A is better, as CV is lower for A.
As per the Sharpe Ratio, Fund manager B is better, as Sharpe Ratio is higher for B.
So, we can have conflicting result from Sharpe Ratio and CV comparison. Since Sharpe Ratio, measures
the excess return relative to Risk, Sharpe Ratio is Preferred over CV.
LOS 7.h. Calculate and interpret the proportion of observations falling within a specified number of
standard deviations of the mean using Chebyshev’s inequality
Ideally, this LOS should have been covered in reading no -9, where we are covering the distribution.
Covering the concept over here would entail some unnecessary hard-ship on you. Leaving this LOS, at
this point of time will not impact the flow of study. So, we will cover this LOS in Reading 9.
LOS 7.j. Define and interpret Skewness, explain the meaning of a positively or negatively skewed return distribution, and describe the relative locations of the mean, median, and mode for a nonsymmetrical distribution
Skewness -Ideally the distribution should be symmetrical around the mean, that is if we put a mirror
along the Y Axis on the mean, the reflection of the left side should be identical to the shape of the right
side. However in real life, we usually do not find symmetrical distribution.
© Knowledge Varsity – 2011
In everyday language, the terms “skewed” and “askew” are used to refer to something that is out of line
or distorted on one side. When referring to the shape of frequency or probability distributions,
“skewness” refers to asymmetry of the distribution.
Skewness is of two types
Positively Skewed –In this case the distribution is skewed to the right side and hence it is also
called as Right Skewed. If you see the diagram given below, you would see that in case of positive
skewed distribution there is a long tail in the right side. The long tail denotes that there are
outliers in the positive side of the distribution, that is, there are some observations which have
large positive value and hence they are able to shift the mean to the right side.
As an example consider that in a class, there is a brilliant student and he scores 100 out of 100 in
the examination, there are 4 other student in the class, who are average and they score 60 marks
each in the examination. The mean marks of the students in the class would be 68, but the mode
and the median are equal to 60. Hence due to the presence of above average student the mean has
shifted to the right.
For this kind of distribution, you will find that the mean is more than median and median is more
than the mode.
Negatively Skewed –In this case the distribution is skewed to the left side and hence it is also
called as Left Skewed. If you see the diagram given below, you would see that in case of negative
skewed distribution there is a long tail in the left side. The long tail denotes that there are outliers
in the negative side of the distribution, that is, there are some observations which have large
negative value and hence they are able to shift the mean to the left side.
An example, here could be the returns in a stock market, many times we observe that there are
some returns which are highly negative and there are more returns which are positive , because of
large negative returns the mean return shift to the left and hence we can see a left skewed
distribution.
Mnemonic: As per dictionary, the order of the words is Mean, Median and Mode. Hence Negative
skewed distribution follows the dictionary order that is, mean is less than median which in turn is
less than mode. Please note that median will always be in the middle.
Important Exam Points for Skeweness
Mean always get shifted in the direction of skewness, for positively skewed distribution, mean is
shifted to the positive side (or right side)
For a symmetrical distribution, the distance from the mean to the highest observation would be
same as that of distance from the mean to the lowest observation.
Concept Builder – Skeweness
19. Suppose the mean is given as 50% and the highest return value is given as 100% and lowest return
value is given as 0%. State whether the distribution is symmetrical or not?
Explanation
Since, here the distance from the mean to the highest value and the distance to the lowest value is
same, we would say that the distribution is symmetrical.
© Knowledge Varsity – 2011 Page 43
20. Suppose the mean is given as 50% and the highest return value is given as 80% and lowest return
value is given as 0%. State whether the distribution is symmetrical or not? If it is not symmetrical
then state whether it is positively skewed or negatively skewed?
Explanation
Since, here the distance from the mean to the highest value is 30 and the distance to the lowest value is
50, then we would say that the distribution is skewed to the left as we have long tail there.
LOS 7.k. Define and interpret measures of sample Skewness and kurtosis
This LOS asks us to define the measure of sample skeweness and kurtosis. In the CFA text book, you
would find that formula for sample skeweness and kurtosis are given, but you don’t have to remember
the formula, since the LOS doesn’t ask you to calculate. However you require interpretation of these.
Skeweness is measure of 3rd moment, that is, we are taking the cube of the deviation from the mean
and summing them up. This result in the following interpretation
o Skewness can range from minus infinity to positive infinity.
o For a symmetrical distribution, skeweness = 0
o For positively skewed distribution, skeweness>0
o For negatively skewed distribution, skeweness< 0
From examination point of view, you just need to know the above and nothing more.
Kurtosis - Kurtosis is a measure of the Peakness of a symmetric distribution as compared to a normal
distribution of the same variance. Here, before covering anything lets cover normal distribution.
Normal Distribution – As of now, just understand that this is one type of distribution which is
symmetrical in nature. It has a kurtosis of 3. We would cover this distribution in detail in the Reading
Number 9.
Kurtosis is of three types:-
Leptokurtic
o This type of distribution is more peaked than the normal distribution.
o The kurtosis of Leptokurtic distribution is more than 3
o In this type of distribution, there is large number of observation which is near the mean and
also large number of observation away from the mean.
o It has fatter and long tails
o Mnemonic -It has a shape like that of small L and L stands for Lepto
Mesokurtic
o A mesokurtic distribution has kurtosis of 3 which is same as normal distribution and hence
mesokurtic distribution is actually a normal distribution. We compare kurtosis with respect
to mesokurtic distribution only.
Platykurtic
o This type of distribution is less peaked than the normal distribution.
o Platykurtic distribution is Flat.
o The kurtosis of Platykurtic distribution is less than 3
o It has thinner and shorter tails
o Mnemonic – Platy can be thought of as “FLAT”, add P in FLAT to get PLAT
© Knowledge Varsity – 2011
Excess Kurtosis – Excess kurtosis tries to find out the kurtosis which is more than that of a mesokurtic
(normal) distribution. Since the Kurtosis for a normal distribution is equal to 3. The excess kurtosis
formula is given by
Excess Kurtosis = Kurtosis - 3
Therefore, Excess Kurtosis for
Leptokurtic distribution is more than 0
Mesokurtic distribution is 0.
Platykurtic distribution is less than 0
Kurtosis Measure: We don’t need to know the formula of Kurtosis; we just need to know that Kurtosis
is the 4th moment. That is kurtosis is calculated by taking the sum of the fourth power of the
deviations. As a result Kurtosis is always positive.
© Knowledge Varsity – 2011 Page 45
Concept Notes For Reading 8- Probability Concepts
Reading Summary
This reading covers important probability concepts. Here we will discuss about random variables,
properties of probability. We will also understand how probability theory is used in betting. From
examination point of view, this is an important reading, because the concepts would be used in
portfolio management and also in the next readings where without understanding of probability it
would be difficult to understand the distributions. Quite a few questions from this reading are expected
in the examination.
From our experience, we have seen that to do well in this topic, you should understand how to
structure a probability problem using a tree diagram. Bayes theorem is a very important topic which
you need to master. However permutation and combination topic can be taken lightly.
LOS 8.a.Define a random variable, an outcome, an event, mutually exclusive events, and exhaustive events
A random variable is a quantity whose observed value is uncertain.
Outcome is the observed value of a random variable.
Event is a specified set of outcomes. It can be a single outcome also.
Mutually exclusive events are those events in which only one of the events would happen at a
particular time. So, in mutually exclusive event it is not possible to observe all the events at one time.
Exhaustive means that the outcome of the events covers the entire possible scenario.
An example of mutually exclusive and exhaustive event would be the pattern of stock price. At any
point of time, the share price would
Increase
Decrease
Stay same
So, the three states given above are mutually exclusive but note that they are collectively exhaustive
because, these are the only states possible. You can’t have a stock’s price changing to some other state.
Mnemonic: MECE – Mutually Exclusive and Collectively Exhaustive
LOS 8.b.Explain the two defining properties of probability and distinguish among empirical, subjective, and a priori probabilities
The two defining properties of probability are as follows:-
1. The probability of any event (E) is a number between 0 and 1, that is,
2. The sum of the probabilities of any set of mutually exclusive and collectively exhaustive event should
be always equal to 1. That is,
Going back to the stock price example of last LOS. It’s not possible to have the probability of any of the
state as negative or more than 1. Let’s say that the probability of increase is 0.4, decrease is 0.5 and
remaining the same is 0.1.
Here we are seeing that the sum of the probabilities of these mutually exclusive and exhaustive events
should be equal to 1.
How do we determine the probability of any set of events?
Estimation of Probability: There are 3 approaches in which we can estimate the probability. The
approach is divided into Objective and Subjective. Objective is further divided into Empirical and Priori
Probability. The following diagram will make the concept clearer.
© Knowledge Varsity – 2011
Let’s cover what these probability mean
Empirical Probability – Empirical probability is estimated using the past data.
Example – Suppose we have seen that over the past 250 trading days. The number of days the stock
price increased was 100. The number of days the stock price decreased was 125 and the number of
days the stock price remained the same was 25.
Now probability is also defined as
So with the historical observation, we can say that the probability that the stock price will increase
will be equal to 100 (no of favorable days) divided by 250 (total number of days), which will be 0.4.
Likewise we can estimate the probability of decrease and remaining same also.
A Priori Probability–A priori probability is estimation of probability using formal reasoning or logical
method.
Example – Suppose, we estimate that the inflation of the economy is high and it is expected that
the central bank will increase the interest rate. In this scenario with formal reasoning we expect
that the probability that the stock price will decrease, we do some analysis and come up with a
probability value of 0.7, and similarly other probabilities.
Subjective Probability–Subjective probability is estimation of probability based on gut feeling. It is
the least formal method and involves lot of subjectivity by the estimator. In investment, its usage is
frequent in nature.
Example – A person may say that in his personal opinion the probability of stock rising the next day
is 0.7.
LOS 8.c.State the probability of an event in terms of odds for or against the event
This LOS covers the concept related to betting. In betting we use the term odds for a team winning etc.
Terminologies
Odds for an event–Out of the total how much is in favor of a particular event.
Example : Odds for India winning against Pakistan is 5 to 3, it implies that out of (5+3 = 8) times,
India will win the match 5 times and Pakistan will win the match 3 times.
Odds against an event - Out of the total how much is against a particular event.
Example : Odds against India winning in a match with Pakistan is 3 to 5, it implies that out of (5+3 =
8) times, Pakistan will match 3 times and India will win the match 5 times .
Note: Odds for an event is just the reciprocal of the odds against the event
In examination, there are 2 types of questions that would be asked
a) Find out the probability, given odds for an event or against an event.
a. If odds for an event is given as A:B then the probability that event A will occur is
b. If odds against an event is given as A:B then the probability that event A will occur is
b) Given probability for an event, find out the odds for or against the event
Probability
Estimation
Objective
Empirical A Priori
Subjective
© Knowledge Varsity – 2011 Page 47
a. If Probability of an event is given as P(E) then the odds for the event is
b. If Probability of an event is given as P(E) then the odds against the event is
Even though we have given the formula, dealing these concepts in formula is not the correct approach,
rather than that you should understand the underlying concept. It would become clear by seeing the
below example.
Concept Builder – Finding probability when Odds For and Odds Against is given
1. The bookies are quoting the following for the final match between Liverpool and ManU
Odds For Liverpool : 7 to 11
What is the probability of Liverpool winning the match? What is the probability of ManU winning
the match?
Explanation
The probability that Liverpool will win the match is its favorable case divided by the total case
P(Liverpool winning) = 7/18 = 0.389
The probability that ManU will win the match is its favorable case divided by the total case
P(ManU winning) = 11/18 = 0.611
Since, This could also be obtained by subtracting P(Liverpool winning) from 1
P(ManU winning) = 1 - P(Liverpool winning) = 1 – 0.389 = 0.611
Needless to say, we are ManU fans!!
Concept Builder – Finding Odds For and Odds Against when probability is given
2. Suppose you determine that the probability of Chennai Super Kings winning a match against
Mumbai Indian is 0.6, then what would be the
a. Odds that Chennai Super Kings will win the match
b. Odds that Chennai Super Kings will lose the match (Note that here we are asking odds
against in an indirect way)
Explanation
a. For finding the odds for; without following the formula; we should think of odds for as
Probability the event will occur : Probability the event will NOT occur
Probability that Chennai will win : Probability that Chennai will lose
0.6 : 0.4 Or 6:4 Or Simplifying it a bit, 3:2
So the odds that Chennai Super Kings will win the match is 3 : 2
b. For finding the odds against; without following the formula; we should think of odds against as
Probability the event will NOT occur : Probability the event will occur
Probability that Chennai will lose : Probability that Chennai will win
0.4 : 0.6 Or 4:6 Or Simplifying it a bit, 2:3
So the odds that Chennai Super Kings will lose the match is 2 : 3
LOS 8.d.Distinguish between unconditional and conditional probabilities
Unconditional Probability: It is also referred as marginal probability. It is the probability that an event
will occur regardless of any past or future occurrence of any other event.
Conditional Probability: The probability that an event will occur, given that one or more other events
have already occurred. More precisely the probability that B will occur given that A has occurred.
The symbol P (B|A) represents Conditional Probability and is read as Probability of B given A has
occurred.
© Knowledge Varsity – 2011
LOS 8.g.Distinguish between dependent and independent events
We will be covering this LOS before we cover LOS 8.e and LOS 8.f
1. Independent Events – These are events in which the occurrence of one event has no impact on the
occurrence of the other events. As an example, your score in an exam is independent of the score
of your friend. In terms of conditional probabilities, two events are independent, if and only if
P(A | B ) = P(A) or P(B | A ) = P(B)
If the condition above is not satisfied then the events are dependent events
2. Dependent Events – These are the events in which occurrence of one event has an impact on other
events. As an example, your score in an exam is dependent on the amount of effort you have put in
to study for the exam.
Here in this section, we will be covering both LOS 8.e and LOS 8.f
LOS 8.e.Define and explain the multiplication, addition, and total probability rules LOS 8.f.Calculate and interpret 1) the joint probability of two events, 2) the probability that at least one of two events will occur, given the probability of each and the joint probability of the two events, and 3)
a joint probability of any number of independent events
a) Multiplication Rule of probability – It is used to find out the Joint Probability of 2 events. Joint
probability is the probability that 2 events would happen together (or simultaneously).
We would see the following type of joint probability in the curriculum.
1. Joint Probability of conditional events
2. Joint Probability of independent events
Let’s cover these two concepts
1. Joint Probability of conditional events –The joint probability of conditional event is given as
Where, is the conditional probability that A will happen, given that B has happened.
And is the unconditional probability of B.
2. Joint Probability of independent events – In case of independent events A and B, the joint
probability is given as
So, the joint probability is the multiplication of the individual probabilities and the multiplication
rule is used to denote the joint probability.
This concept can be extended for any number of independent events
Let’s say that A1, A2, ……, AN are independent events, the probability that all of these events occur
simultaneously is given by
Note that when you see AND , this means that you have to use multiplication.
b) Addition Rule of probability – It is used to find out the probability that at least one of the event will
occur. In case of two events A and B.
Addition rule will say that Event A OR B will occur.
Note that when you see OR, this means that you have to use addition.
You can extend the addition rule concept to determine the probability that at least one of the event
would occur. If you notice the below formula, here we are saying that Either A occurs or B occurs, it
implies that sometimes A occurs, sometimes B occurs or sometime both will occur, it will not happen
anytime that none of the event is occurring.
You can understand this better from the Venn diagram, which is shown below. The shaded region
represent that both A and B will occur together. Note that when we add P(A) and P(B), the shaded
© Knowledge Varsity – 2011 Page 49
region will come twice, hence we need to subtract it from the addition to come up with the true
probability that at least A or B will occur.
c) Total Probability is the probability of occurrence of an event, given conditional probability.
Let’s say there are N mutually exclusive events denoted as A1, A2, ……, AN. Each of these events are
conditional on mutually exclusive and exhaustive events B1, B2, ……, BN.
We can obtain the unconditional probability of event A (which we say is the sum of the probabilities of
each event Ai)
Since A1 is conditional on B1, We can write
Replacing this for all Ai’s we have
The probability of A that we have obtained here is un-conditional probability, that is, it doesn’t depend
on whether B1 is occurring or B2 is occurring.
Hence we can say that Total Probability is used to find out the unconditional probability of an event
when the conditional probabilities are given.
2 Scenario Case: The total probability rule is stated below for a special case involving 2 scenarios. If we
have an event denoted by B, then we will denote the event which is NOT B (or complement of B) with
(spelt as B bar). Here B and are mutually exclusive and collectively exhaustive event.
Let’s say we have an event A, which will occur when B occurs and also when B doesn’t occur. The total
probability for this two scenario case can then be written as
Below is a representation of the total probability concept using tree diagram. Tree diagram is
considered in a separate LOS, but this is ideal place to introduce the concept of tree diagram.
© Knowledge Varsity – 2011
So, from the above diagram, it becomes clear that Node 1 and Node 3, are representative of occurrence
of A, whereas node 2 and node 4 are representative of occurrence of NOT A (or A bar).
If you add the value obtained in Node 1 and Node 3, you will get the probability of occurrence of A.
If you add the value obtained in Node 2 and Node 4, you will get the probability of occurrence of A bar
(or Not A).
The tree diagram will become clearer as and when we solve more problems. We would suggest thinking
about tree diagram when you are solving problems which involve conditional probability because it
gives a better understanding.
Concept Builder – Joint Probability Of Conditional Events and Addition Rule
3. Suppose probability that RBI will decrease the interest rate is 0.6 and the probability that recession will
happen if the interest rate is decreased is 0.3.
A. Find the joint probability of decrease in interest rate and recession?
B. If the probability that either interest rate will decrease or recession will occur is 0.82, find the
unconditional probability of recession
Explanation
A. In notation term we can write ; P(Decrease Interest) = 0.6; P(Recession | Decrease Interest) = 0.3
The joint probability is P(Decrease Interest AND Recession); as per the joint probability for conditional
probabilities we have
P(Decrease Interest AND Recession) = P(Recession | Decrease Interest) * P(Decrease Interest)
P(Decrease Interest AND Recession) = 0.6 *0.3 = 0.18
B. Unconditional probability of recession = P(Recession)
Here we have OR condition
=> P(Recession Or Decrease Interest) = P(Recession) + P(Decrease Interest) – P(Recession AND Decrease
Interest)
=> 0.82 = P(Recession) + 0.6 – 0.18 => P(Recession) = 0.82 -0.6 +0.18 = 0.4
Therefore the unconditional probability that recession will happen is 0.4
Concept Builder – Joint Probability Of Independent Events
4. Suppose that you are tossing a coin 5 times in a row. What is the probability that Head will come in
each of the time?
Explanation
Here , the tossing of coins are independent events . For independent events, we have the following
P(A and B) = P(A) * P(B)
Probability of Head coming in 1 toss = ½ = 0.5
Probability of Head coming in 5 tosses = ½ * ½ * ½* ½* ½ = 0.0312
LOS 8.h.Calculate and interpret, using the total probability rule, an unconditional probability
As we had stated in the last LOS that total probability is also known as unconditional probability. This
LOS specifically asks us to calculate the unconditional probability using the total probability rule.
Many of us are not able to appreciate fact that the total probability is the unconditional probability.
Let’s solve one example to calculate the total probability and understand the concept of unconditional
probability.
Concept Builder – Calculating the Total Probability
5. If you are following the recent events, Reserve Bank of India is increasing the interest rates to
contain the inflation. One of the major drawback of raising interest rate is that the chances that the
economy will go into recession increases. However, it’s not the case that an economy can’t be in
recession if the interest rates are decreased (see USA, even though the interest rates are decreased
in US, the state of the economy is not good).
Coming to the question. Let’s say the probability that the Central Bank would increase the interest
rate is 0.7 and the conditional probability of Recession happening when the interest rate is
© Knowledge Varsity – 2011 Page 51
increased is 0.9. Also, the conditional probability that the recession will happen if the interest rate is
decreased is 0.2.
We are interested in finding out
a) The unconditional probability that the Recession will happen
b) The unconditional probability that the Recession will NOT happen
Explanation
You will find that in book, there is notation to the unconditional probabilities. We will go through this
problem by following those notations, and then try to solve the problem through the formula of the
total probability. In the next step we will try to solve the problem using the TREE DIAGRAM. We advise
the candidates to follow the tree diagram.
Probability of Increase in Interest Rate = = 0.7
Probability of decrease in Interest Rate = = 1 – 0.7 = 0.3
Probability of Recession happening Given Interest Rate Increases =
Probability of Recession happening Given Interest Rate Decreases = = 0.2
Probability of Recession NOT happening Given Interest Rate Increases = = 1 -
= 1 -0.9 = 0.1
Probability of Recession NOT happening Given Interest Rate Decreases = = 1- 0.2 = 0.8
The unconditional probability that the recession will happen is same as the total probability that the
recession will happen.
As per the total probability formula, we can write
=> P(R) = 0.9 *0.7 + 0.2 * 0.3 =0.63 +0.06 = 0.69
So, the unconditional probability that recession will happen is 0.69
The probabilities that you had seen earlier or were conditional probabilities, that is, they
were dependent on whether the interest rate is increased or decreased. But the total probability is not
depended on increase/decrease of interest rate, it doesn’t matter whether interest rate increases or
decreases, if the interest rate increases, then the probability of recession will increase and if the
interest rate decreases then the probability of recession will decreases, but overall the probability will
be the same and hence un-conditional.
We can find the un-conditional probability of recession NOT happening – it will simply be 1 minus the
un-conditional probability of Recession happening.
The unconditional probability that recession will NOT happen = 1 - 0.69 = 0.31
We can also find out the above value using the total probability formula
=> 0.1 *0.7 + 0.8 * 0.3 = 0.07+0.24 = 0.31
Let’s see, how we can solve this using Tree Diagram, You will find it intuitive
© Knowledge Varsity – 2011
While constructing tree diagram,
1st STEP - We start with first the un-conditional probability, which we have here for the Interest rate. So
the first branch will be for the interest rate increase and the other branch is for the interest rate NOT
Increasing.
2nd STEP - Then we start with the conditional probabilities and draw branches for them. Throughout the
process, we will keep in mind that the branches are Mutually exclusive and Collectively Exhaustive.
3rd STEP – We highlight the node is related to the respective probabilities. Here Node 1 and Node 3 are
the nodes for Recession happening and Node 2 and Node 4 are the nodes for Recession NOT
happening.
4th STEP - To find out the Total Probability of recession, we add up the value at the nodes were
recession happens. Therefore Recession probability = 0.63 + 0.06 = 0.69
To find out the Total Probability of recession NOT happening, we add up the value at the nodes were
recession does not happen. Therefore Recession probability = 0.07 + 0.24 = 0.31
This is the way we will be drawing the TREE Diagram and hence finding out the total or un-conditional
probabilities.
LOS 8.i.Explain the use of conditional expectation in investment applications
In previous reading we had covered the concept of Weighted Mean return in a portfolio, which was
based on the weight of the individual asset. We had obtained the weighted mean return by multiplying
the weight of asset with the return of the particular asset. If you think about the Total Probability, it can
also be considered like a weighted mean; here the weight is the conditional probability. We are going to
introduce the concept of Expected value which can be viewed like weighted mean.
Expected Value –Expected value of a random variable is the probability weighted average of the
possible outcomes of that random variable.
Expected value is denoted by E(X) where X is the random variable.
Expected value is a futuristic value and is based on our expectation about the future, it is not
necessary that whatever we are expecting about the future will happen.
The formula for the expected value can be written as
Where, is the outcome of the random variable with a probability of
© Knowledge Varsity – 2011 Page 53
Concept Builder – Finding Expected Value for throw of Dice
6. Find the Value that you would expect when you throw a Six faced dice having numbers from 1 to 6
Explanation
When we throw a dice, we can get any number from 1 to 6. By Expected value we imply what is the
value on an average we will get when we throw a dice.
The random variable can take values from 1 to 6.
The probability that either 1,2,3,4,5 or 6 would come when we throw a dice is 1/6
Hence Expected Value is calculated as,
Therefore we should expect that in one throw we should get on an average 3.5
But 3.5 is not a number that you will observe, we get sometimes 1 and sometimes 6, hence there is
variance in our observation.
We will take up the variance concept after next example.
Concept Builder – Finding Expected Earnings Per Share (EPS) in an investment Setting
7. You are analyzing, Infosys Technologies (NASDAQ: INFY) stock and based on your evaluation you
have come up with the following estimates of EPS for the year 20X2 and the probabilities that the
firm would be able to achieve the EPS. See the table below for the estimates
Probability EPS
0.35 $2.8
0.3 $2.9
0.25 $3.1
0.1 $4
What is the expected EPS of INFY in 20X2?
Explanation
Expected Value is probability weighted
Hence the expected value of EPS is $3.03, so you have estimated that INFY will have EPS of $3.03 in the
year 20X2.
Since, expected value can be considered as mean; hence we will also get variance because there are
times when the value thus obtained will not be equal to the expected value.
Variance –The variance of a random variable is the probability weighted average of the squared
deviations from the expected value. The formula for the variance is given below
Standard deviation is square root of variance.
Concept Builder – Finding Variance and Standard Deviation of an Expected value
8. You are analyzing, Infosys Technologies (NASDAQ: INFY) stock and based on your evaluation you
have come up with the following estimates of EPS for the year 20X2 and the probabilities that the
firm would be able to achieve the EPS. See the table below for the estimates
Probability EPS
0.35 $2.8
0.3 $2.9
0.25 $3.1
0.1 $4
© Knowledge Varsity – 2011
What is the variance and standard deviation of the expected EPS of INFY in 20X2?
Explanation
We have calculated the expected value in the previous example as $3.025
For simplicity, we will calculate the variance using the following table
Probability EPS EPS – Expected Value {EPS – E(X)}2 P * {EPS – E(X)}2
0.35 $2.8 (2.8 – 3.025) = -0.225 0.050625 0.01771875
0.3 $2.9 (2.9 – 3.025) = -0.125 0.015625 0.0046875
0.25 $3.1 (3.1 – 3.025) = 0.075 0.005625 0.00140625
0.1 $4 (4 – 3.025) = 0.975 0.950625 0.0950625
Sum 0.118875
So, the variance (σ2)is 0.118875 ($2)
The standard deviation (σ )= 0.1188750.5 = $0.34478
This is a simple problem and there is a high probability that this would be coming in the exam.
There are lots of pitfalls here, please avoid them
1. Rather than first subtracting the expected value from the observation and then multiplying, many
students they first multiply and then they subtract
2. Many students do not multiply with probability but take the square of the difference and then divide
by the number of occurrence
Conditional Expectation – In investments, many times we expect outcome which is based on some
event (hence conditional), the expected value based on conditional probability is called as conditional
expectation. Let’s say that the expected value of a random variable X is based on a scenario S, then the
expected value is denoted by E(X|S) , that is, X is conditional on S.
Let’s say that X takes on values X1, X2, ……….Xn then the Expected Value for X is given by
If you see, the above formula looks equivalent to the Total Probability Rule. So, the above can be
viewed as the Total Probability rule for Expected Value, when there are N scenarios.
LOS 8.k.Diagram an investment problem using a tree diagram
An investment problem is when we are calculating the EPS, return or any other measure related to
investment. We associate probability to those measures. So, essentially in an investment problem we
are interested in finding out the expected value. Tree diagram is used to represent these problems as it
becomes very easy to solve the problems.
© Knowledge Varsity – 2011 Page 55
Concept Builder – Tree diagram for Investment Problem
9. There is a probability of 0.6 for decrease in interest rate, the probability of stable interest rate is 0.3
and probability of increase in interest rate is 0.1.
A firm may perform well or poorly in all these scenarios.
The probability that the firm will do well when interest rate increases is 0.3 and the EPS is $2.5.
The probability that the firm will do poorly when interest rate decreases is 0.7 and the EPS is $1.5
The probability that the firm will do well when interest rate is stable is 0.5 and the EPS is $3.
The probability that the firm will do poorly when interest rate decreases is 0.5 and the EPS is $2
The probability that the firm will do well when interest rate decreases is 0.8 and the EPS is $4.
The probability that the firm will do poorly when interest rate decreases is 0.2 and the EPS is $3.
A. Draw a tree diagram to represent the above problem.
B. Find out the expected EPS conditional on the firm doing well
C. Find out the expected EPS conditional on the firm doing poor
D. Find out the expected EPS (that is unconditional EPS)
Explanation
B. The Node 1, 3 and 5 represent the Expected EPS conditional on the firm doing well .
The Expected EPS will be the probability weighted of the EPS
C. The Node 2, 4 and 6 represent the Expected EPS conditional on the firm doing well .
The Expected EPS will be the probability weighted of the EPS
D. The expected EPS or the unconditional EPS is given as
LOS 8.n.Calculate and interpret an updated probability using Bayes’ formula
We will cover this LOS before we cover the other LOSs.
Till now we have covered probabilities which are based on our expectation or historical data and were
static. In reality, the probabilities keep on changing as and when new information becomes available.
Bayes’ formula addresses the concept of updated probability. Following is the formula given for the
updated probability
© Knowledge Varsity – 2011
The following is the probability notation
The updated probability is also known as posterior probability.
Rather than focusing on the formula, we will be covering the Bayes’ theorem using the tree diagram.
Concept Builder – Bayes’ Theorem
10. Going back to one of the previous problem. The probability that the Central Bank would increase
the interest rate is 0.7 and the conditional probability of Recession happening when the interest
rate is 0.9. Also, the conditional probability that the recession will happen if the interest rate is
decreased is 0.2.
You want to update your Prior probabilities with some new information
a) Given that recession has happened, what is the updated probability that interest rate was
increased?
b) Given that recession has NOT happened, what is the updated probability that interest rate was
increased?
c) Given that recession has happened, what is the updated probability that interest rate was
decreased?
d) Given that recession has NOT happened, what is the updated probability that interest rate was
decreased?
Explanation
The Tree Diagram is given below.
a) Here, we know that the recession has happened; it means that either Node 1 or Node 3 has
happened. Now since we are interested in finding out the updated probability of increase in interest
rate given that recession has happened. So, if you see the tree diagram, our favorable case is Node 1
and the total case is Node 1 and Node 3.
The probability is given by : favorable case / total case
=> Updated probability = 0.63/(0.63+0.06) = 0.9130
You will appreciate the fact that recession is mainly happening due to increase in interest rate and
hence the updated probability is very high as compared to the prior probability.
b) Here our favorable case is node 2 and total case is node 2 and node 4
© Knowledge Varsity – 2011 Page 57
=> Updated probability = 0.07/(0.07+0.24) = 0.2258
c) Here our favorable case is node 3 and total case is node 1 and node 3
=> Updated probability = 0.06/(0.63+0.06) = 0.087
d) Here our favorable case is node 4 and total case is node 2 and node 4
=> Updated probability = 0.24/(0.07+0.24) = 0.7742
If you take the sum of probabilities found in a) and c) it would come to 1. This implies that the
probability of recession happening is 1 (As we already know that recession has happened)
LOS 8.k.Calculate and interpret covariance and correlation
Variance measures the dispersion of a single random variable. Many times during investment we are
interested in knowing how two variables move with respect to each other. For example, we might be
interested in knowing if the S&P 500 is increasing what would be the behavior of Microsoft stock,
whether it would increase or decrease.
To understand the movement of 2 variables we have Covariance and Correlation as the measures.
Covariance – Covariance measures how 2 variables move with respect to each other. The formula for
the covariance is given below
So, covariance is the expected value of the product of deviation of the two random variables from their
respective expected value (can be thought of as mean).
Properties of Covariance
Covariance values ranges from negative infinity to positive infinity
The covariance of a variable X with itself is the variance of X
If there is no relation between the assets, then the covariance is 0.
The unit of covariance is squared units
Drawback – Covariance is not able to measure the strength of the relationship. Higher Covariance does
not necessarily means that the strength of the relationship is high. As a result we have another measure
known as Correlation.
Correlation Coefficient – It measures the strength of the relationship. Higher correlation value implies
higher strength. The formula for correlation coefficient is given by
Properties of Correlation Coefficient
Correlation coefficient measures only strength of Linear Relationship
Correlation coefficient is unit less
Correlation ranges between -1 and +1
If there is no linear relation between the assets, then the correlation coefficient is 0.
If the correlation coefficient is +1, then the variables are Perfectly Positively Correlated
If the correlation coefficient is +1, then the variables are Perfectly Negatively Correlated
Most of the time we would be using covariance and correlation from investment point of view, so the
returns are used as the random variable.
© Knowledge Varsity – 2011
Concept Builder – Covariance and Correlation
11. You are analyzing two stocks and are trying to find out the expected return. You are predicting that
the economy can be in either good state or bad state. Following table illustrate the return and the
probabilities that you are expecting from the two stocks.
State of the economy Probability Return of A Return of B
Good 0.7 15% 20%
Bad 0.3 10% 5%
Explanation
First we will have to find out the expected returns of A and B
E(RA) = 0.7 *15% + 0.3*10% = 13.5%
E(RB) = 0.7 *20% + 0.3*5% = 15.5%
The following table has the calculation for Covariance
Probability Return of A Return of B RA – E(RA) RB – E(RB) P * {RA-E(RA)} * {RB-E(RB)}
0.7 15% 20% 1.5% 4.5% 4.725
0.3 10% 5% -3.5% -10.5% 11.025
Sum 15.75
So, the covariance is 15.75 %2 or 0.001575
For finding out the Correlation we need to find the standard deviation of A and B
The standard deviation is computed in the following tables
Probability Return of A RA – E(RA) P * {RA-E(RA)} * {RA-E(RA)}
0.7 15% 1.5% 1.575
0.3 10% -3.5% 3.675
Sum 5.25
So, the variance of A = 5.25%2 => standard deviation = 2.2913 %
Probability Return of B RB – E(RB) P * {RB-E(RB)} * {RB-E(RB)}
0.7 20% 4.5% 14.175
0.3 5% -10.5% 33.075
Sum 47.25
So, the variance of B = 47.25%2 => standard deviation = 6.8739 %
So, the correlation coefficient will be given by
So, here we see that the correlation coefficient is the maximum.
LOS 8.l.Calculate and interpret the expected value, variance, and standard deviation of a random variable and of returns on a portfolio
A portfolio of assets will also have expected return and variance similar to the assets itself. The only
thing is that we observe the benefit of diversification in case of portfolio. By diversification we mean
that we are including more assets in the portfolio. If there are 2 assets in a portfolio and the correlation
coefficient between them is less than 1, then the standard deviation of the portfolio is lesser than the
weighted standard deviation of the individual assets.
Asset Weight in a portfolio - The weight of any asset in the portfolio is given by the following formula
Expected Return of Portfolio – The expected return of the portfolio is the weighted average of the
expected return of the individual asset.
© Knowledge Varsity – 2011 Page 59
Variance of the Portfolio – There is a complex formula for the variance of a portfolio having n assets.
For level 1 we are required to remember the variance of 2 asset portfolio.
The variance of a 2 asset portfolio is given by
In terms of covariance, the formula can be written as
Concept Builder – Portfolio Variance
12. A portfolio is made up of 2 assets A and B. The current market value of investment in A is $600 and
current market value of investment in A is $400. Correlation between A & B is 0.3. The standard
deviation of A is 20% and standard deviation of B is 30%. Find out the portfolio standard deviation?
Explanation
First find out the weight of each asset in the portfolio.
Weight of asset A = 600/(600+400) = 0.6 => Weight of B = 0.4
We will use the 2 asset, standard deviation formula.
=> = 374.4
The variance of the portfolio is 374.4 %2
The standard deviation will be square root of the variance = 19.3494%
If, you calculate the weighted average standard deviation it will be 24%
So, you are seeing that the standard deviation of the portfolio is lesser than the weighted average, this
is the benefit of diversification, which we had discussed.
LOS 8.m.Calculate and interpret covariance given a joint probability function
Joint Probability Table: This is a table in which we mention the joint probabilities of the two variables
for a specified set of outcomes. The Joint probability is very neat way to denote the probabilities of
occurrence of return of 2 investments.
Below is an example of a Joint Probability table
Asset RB = x% RB = y% RB = z%
RA = a% A1 A2 A3
RA = b% A4 A5 A6
RA = c% A7 A8 A9
Some Observations from the joint probability table
Here P1 means the probability of A returning a% and B returning x%
The total probability of A returning a% will be the some across the row which will be A1 + A2 + A3
The total probability of B returning x% will be the some across the column which will be A1 + A4 +
A7
The sum of all the Ai should be equal to 1; that comes from the probability property.
Correlation Matrix – In a correlation matrix the correlation between the variables is mentioned. The
usage of matrix is a very clear representation of the correlation and is widely used.
Below is an example of correlation matrix
Asset A B C
A 1
B 1
C 1
© Knowledge Varsity – 2011
You will find that the lower part of the matrix is redundant, because the correlation coefficient between
A and B is same as the correlation coefficient between B and A.
So, in many places you will find that only the top part is mentioned.
Covariance Matrix – In covariance matrix, the covariance between the random variables is mentioned.
Below is an example of covariance matrix.
Asset A B C
A Cov (RA, RA) = Var(A) Cov (RA, RB) Cov (RA, RC)
B Cov (RB, RA) = Cov (RA, RB) Cov (RB , RB) = Var(B) Cov (RB, RC)
C Cov (RC, RA) Cov (RC , RB) Cov (RC, RC) = Var(C)
Like correlation matrix, here also you will find that the lower part of the matrix is redundant.
LOS 8.o.Identify the most appropriate method to solve a particular counting problem, and solve counting problems using the factorial, combination, and permutation notations
There is a very low probability of this section coming in the examination
We will be covering 3 type of formula here
1. Labeling Formula – The number of ways in which n object can be labeled with k different labels,
with n1 of first type, n2 of second type and so on. n1 + n2 + ….. +nk = 1
The formula is given by
2. Selection Or Combination formula – This is used when we are selecting from a group. It is a special
case of labeling formula. Here the order of the selection doesn’t matter. For example if we are
selecting 6 players from 9 players, it doesn’t matter who gets selected first.
The formula is given as or =
Where n is the total number of object and we need to select r object from it.
So, in the example above, n = 6 , r = 9, so the number of ways = 84
3. Permutation – This formula is used when arrangement of the items selected is also important. For
example in a cricket match, let’s say that the player who gets selected first will be the first one to
bat, hence here the order of selection is important.
The formula is given as =
As an example, if there are 9 players and we need to select 6 players and the order of selection is
important, then the number of ways in which it can happen = 60,480
Concept Builder – Counting Problem
13. Your portfolio has 10 mutual funds,
a. You met an investment advisor and he advised to hold 6 mutual funds and sell 4 mutual
funds. In how many ways this can be achieved?
b. In how many ways you can select 3 mutual funds from the 10 funds
c. In how many ways you can sell 3 mutual funds, where the order of selling is important
Explanation
a. The total number of ways in which we can arrange 10 mutual funds is 10!. The total no of ways in which we
can arrange 6 and 4 mutual fund is 6! And 4! respectively.
Here the sequence doesn’t matter, so we are doing double counting by arranging the 6 and 4
mutual funds, which have to be removed.
© Knowledge Varsity – 2011 Page 61
Hence, the number of ways = 10!/(6! * 4!) = 210
Alternatively, we can directly use the labeling formula, because we are labeling 4 mutual funds as
sell and 6 funds as hold.
the number of ways = 10!/(6! * 4!) = 210
b. This is a selection problem, the number of ways in which we can select 3 mutual funds is given by
10C3 = 120
c. Here the order is important. So we will use permutation
No of ways = 10P3 = 720