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Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-1
Chapter 10
Two-Sample Tests
Basic Business Statistics10th Edition
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-2
Learning Objectives
In this chapter, you learn: How to use hypothesis testing for comparing the
difference between The means of two independent populations The means of two related populations The proportions of two independent populations The variances of two independent populations
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-3
Two-Sample Tests
Two-Sample Tests
Population Means,
Independent Samples
Means, Related Samples
Population Variances
Population 1 vs. independent Population 2
Same population before vs. after treatment
Variance 1 vs.Variance 2
Examples:
Population Proportions
Proportion 1 vs. Proportion 2
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-4
Difference Between Two Means
Population means, independent
samples
σ1 and σ2 known
Goal: Test hypothesis or form a confidence interval for the difference between two population means, μ1 – μ2
The point estimate for the difference is
X1 – X2
*
σ1 and σ2 unknown, assumed equal
σ1 and σ2 unknown, not assumed equal
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-5
Independent Samples
Population means, independent
samples
Different data sources Unrelated Independent
Sample selected from one population has no effect on the sample selected from the other population
Use the difference between 2 sample means
Use Z test, a pooled-variance t test, or a separate-variance t test
*
σ1 and σ2 known
σ1 and σ2 unknown, assumed equal
σ1 and σ2 unknown, not assumed equal
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-6
Difference Between Two Means
Population means, independent
samples
σ1 and σ2 known
*
Use a Z test statistic
Use Sp to estimate unknown σ , use a t test statistic and pooled standard deviation
σ1 and σ2 unknown, assumed equal
σ1 and σ2 unknown, not assumed equal
Use S1 and S2 to estimate unknown σ1 and σ2, use a separate-variance t test
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-7
Population means, independent
samples
σ1 and σ2 known
σ1 and σ2 Known
Assumptions:
Samples are randomly and independently drawn
Population distributions are normal or both sample sizes are 30
Population standard deviations are known
*σ1 and σ2 unknown,
assumed equal
σ1 and σ2 unknown, not assumed equal
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-8
Population means, independent
samples
σ1 and σ2 known …and the standard error of
X1 – X2 is
When σ1 and σ2 are known and both populations are normal or both sample sizes are at least 30, the test statistic is a Z-value…
2
22
1
21
XX n
σ
n
σσ
21
(continued)
σ1 and σ2 Known
*σ1 and σ2 unknown,
assumed equal
σ1 and σ2 unknown, not assumed equal
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-9
Population means, independent
samples
σ1 and σ2 known
2
22
1
21
2121
nσ
nσ
μμXXZ
The test statistic for
μ1 – μ2 is:
σ1 and σ2 Known
*
(continued)
σ1 and σ2 unknown, assumed equal
σ1 and σ2 unknown, not assumed equal
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-10
Hypothesis Tests forTwo Population Means
Lower-tail test:
H0: μ1 μ2
H1: μ1 < μ2
i.e.,
H0: μ1 – μ2 0H1: μ1 – μ2 < 0
Upper-tail test:
H0: μ1 ≤ μ2
H1: μ1 > μ2
i.e.,
H0: μ1 – μ2 ≤ 0H1: μ1 – μ2 > 0
Two-tail test:
H0: μ1 = μ2
H1: μ1 ≠ μ2
i.e.,
H0: μ1 – μ2 = 0H1: μ1 – μ2 ≠ 0
Two Population Means, Independent Samples
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-11
Two Population Means, Independent Samples
Lower-tail test:
H0: μ1 – μ2 0H1: μ1 – μ2 < 0
Upper-tail test:
H0: μ1 – μ2 ≤ 0H1: μ1 – μ2 > 0
Two-tail test:
H0: μ1 – μ2 = 0H1: μ1 – μ2 ≠ 0
a a/2 a/2a
-za -za/2za za/2
Reject H0 if Z < -Za Reject H0 if Z > Za Reject H0 if Z < -Za/2
or Z > Za/2
Hypothesis tests for μ1 – μ2
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-12
Population means, independent
samples
σ1 and σ2 known
2
22
1
21
21n
σ
n
σZXX
The confidence interval for
μ1 – μ2 is:
Confidence Interval, σ1 and σ2 Known
*σ1 and σ2 unknown,
assumed equal
σ1 and σ2 unknown, not assumed equal
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-13
Population means, independent
samples
σ1 and σ2 known
σ1 and σ2 Unknown, Assumed Equal
Assumptions:
Samples are randomly and independently drawn
Populations are normally distributed or both sample sizes are at least 30
Population variances are unknown but assumed equal
*σ1 and σ2 unknown, assumed equal
σ1 and σ2 unknown, not assumed equal
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-14
Population means, independent
samples
σ1 and σ2 known
(continued)
*
Forming interval estimates:
The population variances are assumed equal, so use the two sample variances and pool them to estimate the common σ2
the test statistic is a t value with (n1 + n2 – 2) degrees of freedom
σ1 and σ2 unknown, assumed equal
σ1 and σ2 unknown, not assumed equal
σ1 and σ2 Unknown, Assumed Equal
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-15
Population means, independent
samples
σ1 and σ2 knownThe pooled variance is
(continued)
1)n(n
S1nS1nS
21
222
2112
p
()1
*σ1 and σ2 unknown, assumed equal
σ1 and σ2 unknown, not assumed equal
σ1 and σ2 Unknown, Assumed Equal
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-16
Population means, independent
samples
σ1 and σ2 known
Where t has (n1 + n2 – 2) d.f.,
and
21
2p
2121
n1
n1
S
μμXXt
The test statistic for
μ1 – μ2 is:
*
1)n()1(n
S1nS1nS
21
222
2112
p
(continued)
σ1 and σ2 unknown, assumed equal
σ1 and σ2 unknown, not assumed equal
σ1 and σ2 Unknown, Assumed Equal
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-17
Population means, independent
samples
σ1 and σ2 known
21
2p2-nn21
n
1
n
1StXX
21
The confidence interval for
μ1 – μ2 is:
Where
1)n()1(n
S1nS1nS
21
222
2112
p
*
Confidence Interval, σ1 and σ2 Unknown
σ1 and σ2 unknown, assumed equal
σ1 and σ2 unknown, not assumed equal
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-18
Pooled-Variance t Test: Example
You are a financial analyst for a brokerage firm. Is there a difference in dividend yield between stocks listed on the NYSE & NASDAQ? You collect the following data:
NYSE NASDAQNumber 21 25Sample mean 3.27 2.53Sample std dev 1.30 1.16
Assuming both populations are approximately normal with equal variances, isthere a difference in average yield ( = 0.05)?
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-19
Calculating the Test Statistic
1.5021
1)25(1)-(21
1.161251.30121
1)n()1(n
S1nS1nS
22
21
222
2112
p
2.040
251
211
5021.1
02.533.27
n1
n1
S
μμXXt
21
2p
2121
The test statistic is:
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-20
Solution
H0: μ1 - μ2 = 0 i.e. (μ1 = μ2)
H1: μ1 - μ2 ≠ 0 i.e. (μ1 ≠ μ2)
= 0.05
df = 21 + 25 - 2 = 44Critical Values: t = ± 2.0154
Test Statistic: Decision:
Conclusion:
Reject H0 at a = 0.05
There is evidence of a difference in means.
t0 2.0154-2.0154
.025
Reject H0 Reject H0
.025
2.040
2.040
251
211
5021.1
2.533.27t
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-21
Population means, independent
samples
σ1 and σ2 known
σ1 and σ2 Unknown, Not Assumed Equal
Assumptions:
Samples are randomly and independently drawn
Populations are normally distributed or both sample sizes are at least 30
Population variances are unknown but cannot be assumed to be equal*
σ1 and σ2 unknown, assumed equal
σ1 and σ2 unknown, not assumed equal
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-22
Population means, independent
samples
σ1 and σ2 known
(continued)
*
Forming the test statistic:
The population variances are not assumed equal, so include the two sample variances in the computation of the t-test statistic
the test statistic is a t value with v degrees of freedom (see next slide)
σ1 and σ2 unknown, assumed equal
σ1 and σ2 unknown, not assumed equal
σ1 and σ2 Unknown, Not Assumed Equal
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-23
Population means, independent
samples
σ1 and σ2 known
The number of degrees of freedom is the integer portion of:
(continued)
11
22
2
2
2
22
1
1
21
2
22
1
21
n
nS
n
nS
nS
nS
*
σ1 and σ2 unknown, assumed equal
σ1 and σ2 unknown, not assumed equal
σ1 and σ2 Unknown, Not Assumed Equal
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-24
Population means, independent
samples
σ1 and σ2 known
2
22
1
21
2121
nS
nS
μμXXt
The test statistic for
μ1 – μ2 is:
*
(continued)
σ1 and σ2 unknown, assumed equal
σ1 and σ2 unknown, not assumed equal
σ1 and σ2 Unknown, Not Assumed Equal
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-25
Related Populations
Tests Means of 2 Related Populations Paired or matched samples Repeated measures (before/after) Use difference between paired values:
Eliminates Variation Among Subjects Assumptions:
Both Populations Are Normally Distributed Or, if not Normal, use large samples
Related samples
Di = X1i - X2i
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-26
Mean Difference, σD Known
The ith paired difference is Di , whereRelated samples
Di = X1i - X2i
The point estimate for the population mean paired difference is D : n
DD
n
1ii
Suppose the population standard deviation of the difference scores, σD, is known
n is the number of pairs in the paired sample
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-27
The test statistic for the mean difference is a Z value:Paired
samples
n
σμD
ZD
D
Mean Difference, σD Known(continued)
WhereμD = hypothesized mean differenceσD = population standard dev. of differencesn = the sample size (number of pairs)
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-28
Confidence Interval, σD Known
The confidence interval for μD isPaired samples
n
σZD D
Where n = the sample size
(number of pairs in the paired sample)
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-29
If σD is unknown, we can estimate the unknown population standard deviation with a sample standard deviation:
Related samples
1n
)D(DS
n
1i
2i
D
The sample standard deviation is
Mean Difference, σD Unknown
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-30
Use a paired t test, the test statistic for D is now a t statistic, with n-1 d.f.:Paired
samples
1n
)D(DS
n
1i
2i
D
n
SμD
tD
D
Where t has n - 1 d.f.
and SD is:
Mean Difference, σD Unknown(continued)
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-31
The confidence interval for μD isPaired samples
1n
)D(DS
n
1i
2i
D
n
StD D
1n
where
Confidence Interval, σD Unknown
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-32
Lower-tail test:
H0: μD 0H1: μD < 0
Upper-tail test:
H0: μD ≤ 0H1: μD > 0
Two-tail test:
H0: μD = 0H1: μD ≠ 0
Paired Samples
Hypothesis Testing for Mean Difference, σD Unknown
a a/2 a/2a
-ta -ta/2ta ta/2
Reject H0 if t < -ta Reject H0 if t > ta Reject H0 if t < -ta/2
or t > ta/2 Where t has n - 1 d.f.
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-33
Assume you send your salespeople to a “customer service” training workshop. Has the training made a difference in the number of complaints? You collect the following data:
Paired t Test Example
Number of Complaints: (2) - (1)Salesperson Before (1) After (2) Difference, Di
C.B. 6 4 - 2 T.F. 20 6 -14 M.H. 3 2 - 1 R.K. 0 0 0 M.O. 4 0 - 4 -21
D =Di
n
5.67
1n
)D(DS
2i
D
= -4.2
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-34
Has the training made a difference in the number of complaints (at the 0.01 level)?
- 4.2D =
1.6655.67/
04.2
n/S
μDt
D
D
H0: μD = 0H1: μD 0
Test Statistic:
Critical Value = ± 4.604 d.f. = n - 1 = 4
Reject
/2
- 4.604 4.604
Decision: Do not reject H0
(t stat is not in the reject region)
Conclusion: There is not a significant change in the number of complaints.
Paired t Test: Solution
Reject
/2
- 1.66 = .01
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-35
Two Population Proportions
Goal: test a hypothesis or form a confidence interval for the difference between two population proportions,
π1 – π2
The point estimate for the difference is
Population proportions
Assumptions: n1 π1 5 , n1(1- π1) 5
n2 π2 5 , n2(1- π2) 5
21 pp
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-36
Two Population Proportions
Population proportions
21
21
nn
XXp
The pooled estimate for the overall proportion is:
where X1 and X2 are the numbers from samples 1 and 2 with the characteristic of interest
Since we begin by assuming the null hypothesis is true, we assume π1 = π2
and pool the two sample estimates
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-37
Two Population Proportions
Population proportions
21
2121
n1
n1
)p(1p
ppZ
ππ
The test statistic for
p1 – p2 is a Z statistic:
(continued)
2
22
1
11
21
21
n
Xp ,
n
Xp ,
nn
XXp
where
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-38
Confidence Interval forTwo Population Proportions
Population proportions
2
22
1
1121 n
)p(1p
n
)p(1pZpp
The confidence interval for
π1 – π2 is:
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-39
Hypothesis Tests forTwo Population Proportions
Population proportions
Lower-tail test:
H0: π1 π2
H1: π1 < π2
i.e.,
H0: π1 – π2 0H1: π1 – π2 < 0
Upper-tail test:
H0: π1 ≤ π2
H1: π1 > π2
i.e.,
H0: π1 – π2 ≤ 0H1: π1 – π2 > 0
Two-tail test:
H0: π1 = π2
H1: π1 ≠ π2
i.e.,
H0: π1 – π2 = 0H1: π1 – π2 ≠ 0
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-40
Hypothesis Tests forTwo Population Proportions
Population proportions
Lower-tail test:
H0: π1 – π2 0H1: π1 – π2 < 0
Upper-tail test:
H0: π1 – π2 ≤ 0H1: π1 – π2 > 0
Two-tail test:
H0: π1 – π2 = 0H1: π1 – π2 ≠ 0
a a/2 a/2a
-za -za/2za za/2
Reject H0 if Z < -Za Reject H0 if Z > Za Reject H0 if Z < -Za/2
or Z > Za/2
(continued)
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-41
Example: Two population Proportions
Is there a significant difference between the proportion of men and the proportion of women who will vote Yes on Proposition A?
In a random sample, 36 of 72 men and 31 of 50 women indicated they would vote Yes
Test at the .05 level of significance
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-42
The hypothesis test is:H0: π1 – π2 = 0 (the two proportions are equal)
H1: π1 – π2 ≠ 0 (there is a significant difference between proportions)
The sample proportions are: Men: p1 = 36/72 = .50
Women: p2 = 31/50 = .62
.549122
67
5072
3136
nn
XXp
21
21
The pooled estimate for the overall proportion is:
Example: Two population Proportions
(continued)
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-43
The test statistic for π1 – π2 is:
Example: Two population Proportions
(continued)
.025
-1.96 1.96
.025
-1.31
Decision: Do not reject H0
Conclusion: There is not significant evidence of a difference in proportions who will vote yes between men and women.
1.31
501
721
.549)(1.549
0.62.50
n1
n1
p(1p
ppz
21
2121
)
ππ
Reject H0 Reject H0
Critical Values = ±1.96For = .05
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-44
Hypothesis Test for 2
0
df = 15
.05
.05
.95
7.26094 24.9958
H
H
o
a
:
:
2
2
25
25
Excel:
=Chiinv(0.95,15)=7.2609
=Chiinv(0.05,15)=24.996
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-45
Hypothesis Test for 2
0
df = 15
.05
.05
.95
7.26094 24.9958
If or reject H .
If 7.26094 do not reject H .
2 2o
2o
7 26094 24 9958
24 9958
. . ,
. ,
22
2
1 15 281
251686
n S .
.
Since
do not reject H .
2
o
1686 24 995805 15
2. . ,
. ,
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-46
Hypothesis Tests for Variances
Tests for TwoPopulation Variances
F test statistic
H0: σ12 = σ2
2
H1: σ12 ≠ σ2
2Two-tail test
Lower-tail test
Upper-tail test
H0: σ12 σ2
2
H1: σ12 < σ2
2
H0: σ12 ≤ σ2
2
H1: σ12 > σ2
2
*
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-47
F distribution
Test for the Difference in 2 Independent Populations
Parametric Test Procedure
Assumptions Both populations are normally distributed
Test is not robust to this violation Samples are randomly and independently drawn
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-48
F Test for Two Population Variances
1
1
21min
11
2
2
1
1
22
22
21
21
nn
atordeno
numerator
df
df
v
vS
SF
p.372
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-49
Hypothesis Tests for Variances
Tests for TwoPopulation Variances
F test statistic22
21
S
SF
The F test statistic is:
= Variance of Sample 1 n1 - 1 = numerator degrees of freedom
n2 - 1 = denominator degrees of freedom = Variance of Sample 2
21S
22S
*
(continued)
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-50
Critical F value for the lower tail (1-)
F distribution is nonsymmetric. This can be a problem when we conducting a two-tailed-test and want to determine the critical value for the lower tail.
This dilemma can be solved by using Formula
Which essentially states that the critical F value for the lower tail (1-) can be solved for by taking the inverse of the F value for the upper tail ().
1 2
2 1
22 21
1 , , 1 22 2 2, , 2 1 2
1 1 , ( )
/v vv v
SF S S
F S S S
12
21
,,,,1
1
vvvv F
F
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-51
The F critical value is found from the F table
There are two appropriate degrees of freedom: numerator and denominator
In the F table, numerator degrees of freedom determine the column
denominator degrees of freedom determine the row
The F Distribution
where df1 = n1 – 1 ; df2 = n2 – 122
21
S
SF
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-52
F 0
Finding the Rejection Region
L22
21
U22
21
FS
SF
FS
SF
rejection region for a two-tail test is:
FL Reject H0
Do not reject H0
F 0
FU Reject H0Do not
reject H0
F 0 /2
Reject H0Do not reject H0 FU
H0: σ12 = σ2
2
H1: σ12 ≠ σ2
2
H0: σ12 σ2
2
H1: σ12 < σ2
2
H0: σ12 ≤ σ2
2
H1: σ12 > σ2
2
FL
/2
Reject H0
Reject H0 if F < FL
Reject H0 if F > FU
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-53
Finding the Rejection Region
F 0 /2
Reject H0Do not reject H0 FU
H0: σ12 = σ2
2
H1: σ12 ≠ σ2
2
FL
/2
Reject H0
(continued)
2. Find FL using the formula:
Where FU* is from the F table with
n2 – 1 numerator and n1 – 1
denominator degrees of freedom (i.e., switch the d.f. from FU)
*UL F
1F 1. Find FU from the F table
for n1 – 1 numerator and
n2 – 1 denominator
degrees of freedom
To find the critical F values:
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-54
F Test: An Example
You are a financial analyst for a brokerage firm. You want to compare dividend yields between stocks listed on the NYSE & NASDAQ. You collect the following data: NYSE NASDAQNumber 21 25Mean 3.27 2.53Std dev 1.30 1.16
Is there a difference in the variances between the NYSE & NASDAQ at the = 0.05 level?
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-55
F Test: Example Solution
Form the hypothesis test:
H0: σ21 – σ2
2 = 0 (there is no difference between variances)
H1: σ21 – σ2
2 ≠ 0 (there is a difference between variances)
Numerator: n1 – 1 = 21 – 1 = 20 d.f.
Denominator: n2 – 1 = 25 – 1 = 24 d.f.
FU = F.025, 20, 24 = 2.33
Find the F critical values for = 0.05:
Numerator: n2 – 1 = 25 – 1 = 24 d.f.
Denominator: n1 – 1 = 21 – 1 = 20 d.f.
FL = 1/F.025, 24, 20 = 1/2.41
= 0.415
FU: FL:
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-56
The test statistic is:
0
256.116.1
30.1
S
SF
2
2
22
21
/2 = .025
FU=2.33Reject H0Do not
reject H0
H0: σ12 = σ2
2
H1: σ12 ≠ σ2
2
F Test: Example Solution
F = 1.256 is not in the rejection region, so we do not reject H0
(continued)
Conclusion: There is not sufficient evidence of a difference in variances at = .05
FL=0.43
/2 = .025
Reject H0
F
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-57
Two-Sample Tests in EXCEL
For independent samples: Independent sample Z test with variances known:
Tools | data analysis | z-test: two sample for means
Pooled variance t test: Tools | data analysis | t-test: two sample assuming equal variances
Separate-variance t test: Tools | data analysis | t-test: two sample assuming unequal variances
For paired samples (t test): Tools | data analysis | t-test: paired two sample for means
For variances: F test for two variances:
Tools | data analysis | F-test: two sample for variances
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-58
Chapter Summary
Compared two independent samples Performed Z test for the difference in two means Performed pooled variance t test for the difference in two
means Performed separate-variance t test for difference in two means Formed confidence intervals for the difference between two
means Compared two related samples (paired
samples) Performed paired sample Z and t tests for the mean difference Formed confidence intervals for the mean difference
Basic Business Statistics, 10e © 2006 Prentice-Hall, Inc. Chap 10-59
Chapter Summary
Compared two population proportions Formed confidence intervals for the difference between two
population proportions Performed Z-test for two population proportions
Performed F tests for the difference between two population variances
Used the F table to find F critical values
(continued)