Solution

ID: past-exam-of-the-msc-in-advanced-computer-science-course-of-the-university-of-oxford/2021/computational-game-theory/1/b/solution

No: these two strict comparisons violate the independence axiom for lottery preferences. Let denote the certain zero-money lottery. Reduction of compound lotteries gives
For example, the second expression assigns probability to the nonzero reward and to zero. The claimed must therefore imply
which is , contradicting the other claimed strict preference.
The same obstruction is visible in any proposed expected utility representation. Subtract from the utility function, and write and . The first comparison requires , hence , whereas the second requires . No real satisfy both. This argument requires neither risk neutrality nor an assumption that the utility function is increasing in money.

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