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Game Theory Lecture 3. Game Theory Lecture 3. 0. 6. 1. 1/6. 4. 5. 3. 2. 1. 1. 1. 1. 1. 1. N.S. S. D,W. D,W. D,W. D,W. D,W. D,W. L,W. 2. 2. 2. 2. 2. W,D. W,D. W,D. W,D. W,D. W,L. 1. 1. 1. 1. D,W. D,W. D,W. D,W. L,W. 2. 2. 2. W,D. W,D. W,D. W,L.
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Game Theory Lecture 3 Game Theory Lecture 3
0 6 1 1/6 4 5 3 2 1 1 1 1 1 1 N.S. S D,W D,W D,W D,W D,W D,W L,W 2 2 2 2 2 W,D W,D W,D W,D W,D W,L 1 1 1 1 D,W D,W D,W D,W L,W 2 2 2 W,D W,D W,D W,L 1 1 D,W D,W L,W 2 W,D W,L
A Lottery 2 2 2 W,D W,D W,D S. W,L 1 1 N.S. S D,W D,W L,W N.S. 2 N.S. W,D W,D S W,L W,L
A Lottery consider the lottery ? for S. N.S. assume that
2 2 2 W,D W,D W,D S. W,L 1 1 N.S. S D,W D,W L,W N.S. 2 W,D W,L
N.S. 2 2 2 S. W,D W,D W,D W,L W,L 1 1 N.S. S D,W D,W L,W L,W 2 W,D W,D W,L
N.S. ? S.
von Neumann - Morgenstern utility functions A consumer has preferences over a set of prizes and preferences over the set of all lotteries over the prizes
4. if then:
we now look for a utlity function representing the preferences over the lotteries
take a lottery: Replace each prize with an equivalent lottery
define: the expected utility of the lottery clearly U represents the preferences on the lotteries
<
If is a vN-M utility function then is a vN-M utility function iff A utility function on prizes is called a von Neumann - Morgenstern utility function if the expected utility function : represents the preferences over the lotteries. i.e. if U is a utility function for lotteries.
If is a vN-M utility function then is a vN-M utility function iff • It is easy to show that if u( ) is a vN-M utility function • then so is au( )+b a>0 2. Let v() be a vN-M utility function. Choose a>0 ,b s.t.
since f( ) is a vN-M utility function, and since for all j It follows that: But by the definition of f( ) hence:
Neumann Janos John von Neumann 1903-1957 Oskar Morgenstern 1902-1976 Kurt Gödel
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