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Old 11-23-2004, 03:01 PM
fnord_too fnord_too is offline
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Join Date: May 2004
Location: Norfolk, VA
Posts: 672
Default Re: odds of losing half your bankroll

Probability of losing half your bankroll is the same as losing 2/3 of the bets. Lets call it losing 33 and winning 17 for simplicity's sake. The probability of this happening is:

C(50,33) * .495^33 * .505^17

For losing AT LEAST half, you need to sum from i = 33 to 50 for
C(50,i) * .495^i * .505^(50-1)

It seems related to RoR, but I really haven't looked at those equations.

For winning 2/3, just swap 33 and 17 in the first equation. ( C(50,33) = C(50,17), so you don't really need to swap that one.)
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