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Subject: Re: Some stats...

Author: Bob Durrett

Date: 17:58:51 01/23/04

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On January 23, 2004 at 20:37:02, Christophe Theron wrote:

>On January 23, 2004 at 14:31:59, Bob Durrett wrote:
>
>>On January 23, 2004 at 14:20:43, Christophe Theron wrote:
>>
>>>On January 23, 2004 at 07:08:07, Kolss 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
>>>>>>%.
>>>>>>
>>>>>>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.
>>>>
>>>>Well, as my former English teacher used to say:
>>>>
>>>>"I'm talking to the trees - but they aren't listening to me..." :-)
>>>>
>>>>I guess some people just don't bother trying to consult a *basic* statistics
>>>>book before jumping on you... ;-)
>>>>
>>>>Best regards - Munjong.
>>>
>>>
>>>
>>>Please don't leave the forum and help me educate people! :)
>>>
>>>Actually people do not need to understand all the maths behind the stats (I
>>>don't myself), but just to understand a few basics. For example that a 10 games
>>>match tells mostly nothing.
>>>
>>>
>>>
>>>    Christophe
>>
>>Imagine yourself playing a 10 game rated match against one of your peers
>>[someone who sneers and blows smoke in your face] and suppose you lost all ten
>>games?  You would then think the match meant a lot!  One step away from that
>>would be when the match were played between your chess program and someone
>>else's.  Your program would be your "pride and joy" and would, in effect, be
>>your surrogate.  I imagine that it would be hard to accept the idea that a ten
>>game loss would be insignificant.  It's great to be able to stand back and see
>>things objectively, of course.  Generally, I feel that SOME information is
>>provided by every tournament or match no matter how few games are played.  I
>>agree in principle, however, that a 5 1/2 to 4 1/2 result in a ten game match
>>would offer little insight into the current playing strengths of the players.
>>
>>Bob D.
>
>
>
>Your last sentence is what I had in mind. 5.5-4.5 as we see so often is not a
>result that allow us to decide which program is better. Even 6.5-3.5 does not
>allow it. And that's what we see all the time, even between programs that are
>supposed to be of very different strength.
>
>So for all practical cases here, a 10 games match is not something I would
>consider interesting.
>
>Of course it can be interesting to replay the games, but for different reasons.
>
>
>
>    Christophe

Yes, I see your point and I agree.

For SMALL tournaments, exhaustive post-mortem analysis of the games may be the
**only** way to obtain a significant amount of useful information from the
tournament.

Bob D.



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