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Subject: Re: Some stats...

Author: Rolf Tueschen

Date: 18:02:19 01/22/04

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On January 22, 2004 at 20:15:14, Rolf Tueschen wrote:

>On January 22, 2004 at 12:53:16, Christophe Theron wrote:
>
>>On January 21, 2004 at 20:00:12, Kolss wrote:
>>
>>>Hi,
>>>
>>>How many games you need depends on what you want to show, of course... :-)
>>>If my calculations are correct, I get the following:
>>>
>>>Shredder 8 vs. Shredder 7.04:
>>>
>>>+90 -65 =145
>>>
>>>=> 162.5 - 137.5
>>>
>>>=> 54.17 %
>>>
>>>=>
>>>Elo difference = +29
>>>95 % confidence interval: [+1, +58]
>>>
>>>That means that based on this 300-game match (for this particular time control
>>>on this particular computer with these particular settings etc.), your best
>>>guess is that S8 is 29 Elo points better than S7.04 (highest likelihood for that
>>>value); there is a 95 % chance that S8 is between 1 and 58 Elo points better;
>>>and the likelihood that S8 is (at least 1 Elo point) better than S7.04 is 97.5
>>>%.
>
>
>This is wrong. Stats doesn't work this way. In your example above 1 Elo is as
>probable as 58 Elo. There is no way to hypostate that Elo 29 is the "best"
>guess. With a defined confidence int. of 95% you get a variance of 1 to 58 Elo
>points. Then you look how your results are differing for two progs. All results
>between 1 and 58 tell you nothing about differences! You still have to admit
>that the two progs could be equally strong. You need at least Elo +-59

[correction: you need simply 59 for the difference between progs] for a
>claim of being better.

>- NB you propose that the two progs are equally
>strong and then you test against it. You must top 58. [all this on the base of a
>specific N of games, the results calculated in Elo; I didn't follow the debate
>but normally you calculate with scores from the games/matches just for
>mentioning it]
>
>Rolf
>
>
>>>
>>>So if you "only" want to show that S8 is better, you can - statistically
>>>speaking - stop now. If you want to "prove" that it is more than 20 Elo points
>>>better, you need a few more games indeed...
>>>
>>>Best regards - Munjong.
>>
>>
>>
>>It's great to see that at least one guy is able to correctly interpret match
>>results here.
>>
>>I hope you will post more often on this subject. Information on it is very much
>>needed here.
>>
>>
>>
>>    Christophe



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