Quote:
Originally Posted by Pyromantha
I don't understand how a utility function could not exist. Perhaps the OP hasn't explicitly calculated what his looks like, but regardless it will exist for him, and ignoring really absurd scenarios, it will be concave downwards.
I take the lottery in your example. Others may take the cash. This example is not similar to what the OP is asking about though, as the lottery is more +EV than the fixed cash alternative. More like the OPs would be to say you have the choice between an instant $5, or a lottery which will give you $1m one time out of a million.
I still have to make my point. You would take the lottery ? Fine, I wouldn't. Neither would a lot of people who will better take the sure money than the unsure one, whatever EV it is. Especially since $100k is quite a few for a lot of us. People maximize utility, not EV (as you can witness in the bubble of expensive tournaments).
Utility functions are assumed to be well behaved. But utility functions are functions of what parameters ? Let's assume for a moment that it be a function of the expected value and standard deviation of the proposal (as in the lottery example). A poker player will routinely order the proposals as follows :
- A is better than B when EV(A) > EV(B)
- if EV(A) = EV(B) then A is better than B when SD(A) < SD(B)
(- if EV(A) = EV(B) and SD(A) = SD(B) then A is better than B if I have more fun playing A than B)*
Exercise : Show that any utility function associated with this ordering is not continuous (and therefore cannot be concave or quasiconcave).
And, by the way, in this case you can build a utility function (function of EV and SD), although mathematically ill-behaved. I could build real-world example of lottery situations where people's choice cannot be determined by the maximisation of a function of EV and SD.
* The point inside parentheses is here to explain to some people why I always push all in every hand when there is no money involved.