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Subject: Re: Maybe a stupid experiment...

Author: David Rasmussen

Date: 16:00:15 01/03/01

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On January 03, 2001 at 09:52:06, José Carlos wrote:

>  Lately, people have been talking here about significant results. I'm not
>really sure if probabilistic calculus is appropiate here, because chess games
>are not stocastic events.
>  So, I suggest an experiment to mesure the probabilistic noise:
>
>  -chose a random program and make it play itself.
>  -write down the result after 10 games, 50 games, 100 games...
>
>  It should tend to be an even result, and it would be possible to know how many
>games are needed to get a result with a certain degree of confidence.
>  If we try this for several programs, and the results are similar, we can draw
>a conclusion, in comparison with pure probabilistic calculus.
>
>  Does this idea make sense, or am I still sleeping? :)
>
>  José C.

It is assumed that a chess game can be regarded as a bernoulli experiment, with
the probability p for winning and 1-p for losing. The same assumption is made in
the rating system.

While not perfectly consistent, the idea is extended so that the distribution of
wins in n games will be binomial. This is not really the case, as p is not
constant, at least not when humans are involved. I believe this to be true too
for computers. But a series of n bernoulli experiments (that will be binomial
distributed) will approach the normal distribution as n grows, and also if p
fluctuates around the some value p_0, we will not really have a binomial
distribution, but as n grows, the distribution will approach the same normal
distribution as if p was equal to p_0 all the time. So it still helps to play
lots of games. In the case where p fluctuates (which is the case in practice
IMO), you will just have to play even more games, than if p was fixed.



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