
Originally Posted by
donjuan
Basically you hate money if you don't put this on a big dog.
I'll just add that with any bet sizing decision true optimal strategy will ultimately depend on the size of the bettor's bankroll (relative to the freeplay), and the availability of hedge bets.
If the freeplay can only be used in a single go, then if we assume zero time value of money and a bettor unable to hedge:
let f = freeplay (as % of bankroll)
let v = bet EV
let d = decimal odds
As win probability = (1+v)/d, the player then seeks to maximize:
E(U) = (1+v)/d*ln(1+(d-1)*f)
with respect to v & d (which together jointly define a bet).
If we further assume EV doesn't vary with odds magnitude then we have:
E(U) = ln(1+(d-1)*f) / d
So to give a few examples for a $50 indivisible freeplay:
Code:
Optimal Odds Optimal Odds
Bankroll (full-Kelly) (quarter-Kelly)
$100 +231* -115*
$1,000 +665 +301*
$10,000 +2,033 +984
$100,000 +6,358 +3,146
Of course a player may always guarantee himself a 75% conversion on his freeplay by betting a 3-team parlays all 8-ways (yielding full-Kelly utility of ln(1+.75f)), and in the cases marked by an asterisk above (assuming zero EV on the bets), that's exactly what he would optimally do.
Anyway, there are obviously tons of enhancements that could be made to this methodology (for example, taking into account that many freeplays may be split up into multiple wagers and that EV typically does vary with odds magnitude), but the general idea is clear.
While players will generally want to select large dogs for their freeplays, there will nevertheless be a limit to the magnitude of the odds a player is willing to accept. Sufficiently small players will optimally choose to use the 8-parlay method for their freeplays in preference to betting underdogs
While higher EV players won't optimally select higher magnitude odds (again we're assuming EV doesn't vary with d), they will obviously be more willing to use their freeplays for underdog betting rather than for an 8-parlay 75% conversion.