betting rates - can they be useful? magdalena hykšová ctu prague 2011
TRANSCRIPT
BETTING RATES
- CAN THEY BE USEFUL?
Magdalena Hykšová
CTU Prague
2011
Which pair has the greates chance for the win
in the competition StarDance 2010?
e.g., Kříž/Stodůlková: stake 1 EUR win 2,55 EUR or nothing
Similarly in the following cases:
Where should we bet for the football match
Spain – Honduras
at the world championship 2010?
Betting shop 1 (S wins) X (draw) 2 (H wins)
Bet-at-home 1,11 8,00 15,00
Fortuna 1,12 6,70 13,00
Tipsport 1,13 8,10 15,05
Numbers in the table:
how much the bookmaker’s pays for 1 EUR in the case of the sake on the right result
Where should we bet for the football match
Spain – Honduras
at the world championship 2010?
Betting shop 1 (S wins) X (draw) 2 (H wins)
Bet-at-home 1,11 8,00 15,00
Fortuna 1,12 6,70 13,00
Tipsport 1,13 8,10 15,05
Whatever happens, Tipsport pays the most
The highest chance for the win: Spain
We bet for all alternatives to obtain 100 EUR in any case.
How many percent of the stake will we get back?
Betting shop 1 X 2 Return
Bet-at-home 1,11 8,00 15,00
Fortuna 1,12 6,70 13,00
Tipsport 1,13 8,10 15,05
Return – e.g., for Fortuna:
To win 100 EUR in the case of the win of Spain,
we have to bet 100/1,12 on it
In total we pay: 00,13
1100
70,6
1100
12,1
1100Z
We bet for all alternatives to obtain 100 EUR in any case.
How many percent of the stake will we get back?
Betting shop 1 X 2 Return
Bet-at-home 1,11 8,00 15,00 91,53 %
Fortuna 1,12 6,70 13,00 89,36 %
Tipsport 1,13 8,10 15,05 93,04 %
Return – e.g., for Fortuna:
In total we pay: 00,13
1100
70,6
1100
12,1
1100Z
% 36,898936,0
00,13
1
70,6
1
12,1
11
Z
100
betting rate p
... how much the bettor has to bet on the event A to win 1 EUR, if A occurs
Hockey championschip 2010, final CZE – RU
pCZE = 1/4, pRU = 9/10
To win S = 100 CZK, I have to bet
100 1/4 = 25 EUR ... win of the Czech Republic
100 9/10 = 90 EUR ... win of Russia
% 87115
100
betting rate p
... how much the bettor has to bet on the event A to win 1 EUR, if A occurs
Hockey championschip 2010, final CZE – RU
pCZE = 1/4, pRU = 9/10
To win S = 100 CZK, I have to bet
100 1/4 = 25 EUR ... win of the Czech Republic
100 9/10 = 90 EUR ... win of Russia
I will pay 115 EUR, win 100 EUR
return:
Hockey championschip 2010, final CZE – RU
pCZE = 1/4, pRU = 9/10
To win S = 100 CZK, I have to bet
100 1/4 = 25 EUR ... win of the Czech Republic
100 9/10 = 90 EUR ... win of Russia
I will pay 115 EUR, win 100 EUR
return:
pCZE + pRU > 1 the bettor loses
fair bett
% 87115
100
FAIR BETT
the bookmaker specifying p must be in danger of getting into the role of the better
we admit positive and negative betts values
the bettor pays: pCZE S + pRU S, obtains: S
pCZE + pRU > 1 ... bettor chooses S < 0 and wins
pCZE + pRU < 1 ... bettor chooses S > 0 and wins
pCZE + pRU = 1
FAIR BETT
S ... the value of the win if A occurs
(positive or negative)
Bettor’s profit: Z(A) = S – pS = (1 – p) S
Z(A) = – pS
In total we can write: Z = (|A| – p) S
For n events:
Z = (|A1| – p1) S + (|A2| – p2) S + ... + (|An| – pn) S
Bookmaker’s estimation of probability P(A):
e.g., P(A) = 0,5
no danger of changing the roles
it is profitable to propose e.g. p = 0,75
Consider S = 100
win 100 CZK if A occurs ... bett 75 EUR
repetition: bookmaker’s guess about bettor’s profit
ca. 1/2 cases: A occurs Z = 100 – 75 = 25 EUR
ca. 1/2 cases: A does not Z = – 75 EUR
Average profit: URE 25755,0255,0Z
Bookmaker’s estimation of probability P(A):
Mean bettor’s profit:
S > 0 mean bettor’s profit Z < 0
bookmaker benefits
fair bett
Fair bett: we allow S < 0
p ... probability that the bookmaker frankly assigns to the event A
S)p)A(P()pS))(A(P1(S)p1)(A(PZ
BETTING RATES DETERMINATION
bettor’s profit: Z(A) = S – pS = (1 – p) S
Z(A) = – pS
coherent betting rates:
profit Z cannot be always positive, no matter
which event occurs (sure win of the bettor)
coherence requirement basic axioms of probability theory
i.e., to prevent a sure loss, bookmaker’s rates p
have to satisfy axioms of probability theory
BETTING RATES
Warning – who can profit from them?
Application of probability
– determination of rates
(although the bets are not fair)
The meaning of axioms of probability theory
Broadening of probability conception
SUBJECTIVE INTERPRETATION
PROBABILITY
= measure of personal conviction or belief
in the occurence of some event
Václav Šimerka (1818 – 1887), 1882
Frank Plumpton Ramsey (1903 – 1930), 1931 (1926)
Bruno de Finetti (1906 – 1985), 1931, 1937
Leonard Jimmie Savage (1917 – 1971), 1954
SUBJECTIVE INTERPRETATION
Everyday considerations
• No traffic jam probably occurs on the highway this time.
• Our hockey team has no chance against Russia.
• This drug should be effective in your case.
• The election will be probably won by CSSD.
• If I set out at 16:10, I will perhaps catch the train.
• CNB predicts the 1.8% VAT grow in 2012.