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Subject: Re: Statistics and Test results

Author: Chris Welty

Date: 00:29:51 10/08/04

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On October 08, 2004 at 01:10:59, Rick Bischoff wrote:

>I did some more research on this--
>
>We are assuming here that an engine's win percentage follows a binomial
>distribution with probability p. meaning that, out of "n" games played (with no
>draws), we can expect the engine to win n*p games on average.

Right.

>3) the interval is then given approximately by:
>
>phat +/- z(a/2) sqrt (  phat * (1-phat) / n )
>

This is usually a pretty good approximation. It's even better if you use it in
reverse and calculate the confidence interval for phat from the known
null-hypothesis value; in this case the the null-hypothesis is that the engines
are equal strength (i.e. win percentage 0.5) and so the confidence interval for
phat is
z(a/2)+/-sqrt(0.5*0.5/n)



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