Kelly with non-binary outcomes

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  • Gonski
    SBR Rookie
    • 07-21-09
    • 2

    #1
    Kelly with non-binary outcomes
    Can anyone provide me with the formula for expected value (as opposed to expected growth) for n bets?

    Additionally, does anyone have any literature on applying Kelly to non-binary outcomes? Preferably for multiple simultaneous, non-binary outcomes?
  • Ganchrow
    SBR Hall of Famer
    • 08-28-05
    • 5011

    #2
    Originally posted by Gonski
    Can anyone provide me with the formula for expected value (as opposed to expected growth) for n bets?
    Since EV is additive across multiple bets (as is the log of expected growth), it's all rather straightforward:

    If the EV for the ith bet is given by EVi, then the total EV across all n bets would be simple be:

    Where if we assume m > n different possible outcomes such that Xi;j is the outcome of bet i given outcome j, and pj is the probability of the occurrence of outcome j then for a given i such that 1 ≤ i ≤n:

    Putting it all together then gives us:
    }

    Originally posted by Gonski
    Additionally, does anyone have any literature on applying Kelly to non-binary outcomes? Preferably for multiple simultaneous, non-binary outcomes?
    Perhaps this post (attached spreadsheet) of Simultaneous Event Kelly (Mut Ex) with changing prices might be of some use at getting you started?
    Comment
    • Pancho sanza
      SBR Sharp
      • 10-18-07
      • 386

      #3
      How does one adjust a group of 5 team teasers that all have the same leg in them.

      Example:


      WinProb20 %Payout5.0Bankroll50000

      Say I have 4 teasers, all with the same win prob & payout as above.

      Full Kelly says bet $1000 on each teaser.

      However given that 1 team that is unique to all the teasers, this would increase risk somewhat.

      Given that, how do I adjust the bet sizes?
      Comment
      • Gonski
        SBR Rookie
        • 07-21-09
        • 2

        #4
        Thanks very much for your reply Ganchrow.
        I think I have it.
        If I use an example you used in a previous blog:
        For a player betting at an edge of 5% and odds of -200, the proper Kelly stake is 10%. Over 100 bets, he has an expected return of 64.7% with a 36.7% probability of not turning a profit and a 3.4% probability of losing two-thirds or more of his stake.

        For a player betting at the same 5% edge but at odds of +400, were he to bet the 10% stake of the -200 player, while he’d have the identical 64.7% expectation, he’d have a 73.5% probability of no profit, while his probability of losing two-thirds or more of his stake would be 55.8%.

        (If no formulae are visible below, then I don't know how to copy formulae drafted in Word to the Blog, any suggestions welcome.) Please see attacment for full copy of reply.

        Then: 12EV=i=1nj=1mpj*Xi;j'>
        Where: 12pj=n!j!n-j!* pj1-pn-j'>
        12Xi;j=1+O-1* k%j* 1-k%n-j-1'>

        And: n = number of bets
        j = outcome or number of wins
        O = Decimal Odds
        k% = % of bankroll bet
        p = probability of winning = ( E +1 ) / O
        m = n +1
        Then I exactly match your results – thank you!

        Where I was getting stuck was that I kept thinking that win sequence had to have an impact on EV. What dawned on me is that it is only relevant if you bet a set dollar (as opposed to %) amount
        12>1n*B'> OR you start factoring in the time value of money (which is only relevant over longer periods of time or when interest rates are very high).

        Can I confirm that the formula for Expected Growth (EG) is:
        12EG=(1+O-1*k%)n*p* (1-k%)n1-p-1'>
        And that the Expected Growth for the above two examples is:
        EGa = 28.98%
        EGb = -71.57%
        Attached Files
        Comment
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