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Subject: Re: crafty beats fritz6 15-9

Author: Michael Neish

Date: 19:41:57 01/18/00

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>Walter expressed surprise at the result as well, since it differed from his
>previous experiment.  It just goes to show that a single experiment is hardly
>conclusive.  OTOH, considering the blitz ratings crafty gets on internet
>servers, it is no slouch in that department.

I keep intending to analyse the statistical variation that one would
expect in the result from a series of games, and never get down to it.
I wonder what Elo's book has to say about it (I don't have a copy).
I sat down the other day and messed about with a few numbers, and found
that if two computers of exactly equal strength play each other over
20 games, then, assuming there are no draws, you would expect a 50-50
score to occur only about 12% of the time, i.e., one in eight matches.
That is, seven matches out of eight will be won by one or the other
computer!  And you could even expect a 12-8 score about 6% of the time,
which is about one in seventeen.  So an equal score will occur only
about twice as often as a lopsided 12-8 score!  I suspect this is old
hat, but a lot of people seem to overlook this fact when apparently
"strange" results appear.

Does someone have a more thorough analysis of this kind of statistics?

If not, then I'll have a go at it later this week, including draws and
different expectations between White and Black, and send another post.
I'm also interested in determining how many games are needed to
establish, to 95% or 99% certainty say, which program is better.

My argument is that statistics are probably good enough to explain the
15-9 score.

What do others think?

Cheers,

Mike.





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