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Subject: unlikely rows in tourneys...

Author: Stefan Zipproth

Date: 10:49:24 01/29/04

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>>1   Fritz 8
>>½½0½1½0000000½1½00101½010½10½110½11011111111000110½01½11½½½1½10½100½½101110½1½½½0½101½001011½½001010
>>51.5/100
>>2   Shredder 8
>>½½1½0½1111111½0½11010½101½01½001½00100000000111001½10½00½½½0½01½011½½010001½0½½½1½010½110100½½110101
>>48.5/100
>>
>>Note, that there is one 8 and one 7 wins in row - stunning, when engines are so
>>similar in strength.
>
>I'm not sure if I like this very much. The highest thing under that is one time
>000 and 111 each. But statistically, I think that lower chains should be more
>frequent. So when it goes 7 or 8 in a row, I would be very suspicious, and try
>to check out many possible reasons.
>>
>>Jouni

Why? I'm testing permanently, and rows are perfectly normal. From a mathematical
point of view, the probability for a row of length n is approximately
0.33^(n-1). (with n=1, this makes 100 %)

So if you play 8 games the probability that all have the same result is about
0.05 %. Within a series of 100 games, this probability raises to a value that is
still unlikely, but no reason for doubts. A row of 4-5 games in a tourney of 100
games can be expected. That's the reason why a test of 10 games says nothing,
imagine this row was at the beginning of the tourney, which is of course
possible...

Of course the above formula bases on two approximations: the probabilities for
win, loss and draw are each 33 %, and the two engines are of equal strength.

Regards,
Stefan



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