Tuesday, October 29, 2013

[ocisjmzf] Win by square root

Match structures of increasing difficulty to win:

1. Best of 7.
2. Unlimited number of games.  First to achieve a 4 game lead.
3. At least 4 games but no upper bound.   Let n be the number of games so far.  First to achieve a lead of 2*sqrt(n).

The last one is equivalent to statistically rejecting the hypothesis that both contestants are equal.  Some possible winning margins: 4-0, 7-1, 9-2, 11-3, 12-4.  Assuming they are not equal, someone will eventually win with probability 1.

Each has been tuned so that 4-0 is a win.  The standard deviation is sqrt(n/4), so 2 square roots is 4 deviations from the mean (assuming equal contestants).  p value 6.3e-5, making the normal approximation to binomial.

With margin only 1 square root, winning scores 1-0, 3-1, 5-2, 6-3, 8-4, 9-5. 2 standard deviation p value 0.046.

Could be used for chess, but need to figure out what to do with draws, in particular, whether a sufficiently high draw rate causes the match to probabilistically go on forever.

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