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Subject: Re: I just don't get this ...

Author: Bo Persson

Date: 04:09:12 01/04/04

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On January 04, 2004 at 05:57:37, George Tsavdaris wrote:

>On January 04, 2004 at 00:42:02, Christophe Theron wrote:
>
>>On January 03, 2004 at 20:53:39, Rick Rice wrote:
>>
>>>Person A posts a message saying Ruffian 2.0 is very dissapointing, with the
>>>results to back it up. This is followed by a second post which basically says
>>>that Ruffian 2.0 rocks with some results to back it up. Are these programs
>>>really so time and hardware sensitive, so as to show varying results on
>>>different CPUs/time controls?
>>>
>>>Ideal solution would be for SSDF to have one massive board with one CPU and
>>>memory for each program (equal CPU and mem for all the progs on its list) and
>>>some way to automate the play of these programs against each other..... on
>>>different time controls such as regular, blitz etc. Just wishful thinking for
>>>the future, but it would eliminate the multiple and varying results.
>>>
>>>Cheers,
>>>Rick
>>
>>
>>
>>Statistics are extremely important in chess, and in computer chess.
>>
>>Unfortunately, even after years of talks about the subject, almost nobody on
>>this message forum understands that you really need A LOT OF GAMES to start to
>>have an impression of a probability about which program is stronger.
>>
>>The variations you have noticed do not come from different setups.
>>
>>These variations are statistical variations. That means that most of the match
>>results posted here are statistically MEANINGLESS.
>
>It would be better, if you first define when something is statistically
>meaningless.
>
>>
>>People love to proudly post the result of the 20 games match they have run
>>overnight. They don't even care to know if that result has any meaning. Well in
>>most of the cases the result means nothing (just a waste of electric power) and
>>you should not care about it at all.
>
> Always the result mean something. If someone play a match with parameters AA
>between engine X and Y, Z number of games, then we are able to conclude some
>things.
> For example that X is stronger than Y with a probability k % (0<k<100)
>when these two play with AA parameters.
>
> You say "most of the cases the result means nothing", so with that, you believe
>that there are some cases(parameters AA,games Z) that the result means
>something.

I think Christophe means that if k% is not big enough, we don't really know
meaning of the result.


> And that for all other parameters AA, games Z the results are meaninless.
>Why? Who can define the right parameters AA, number of games Z? Perhaps the god?

No, but a statistician can tell you how many samples are needed to reach a
conclusion with a specific certainty.

The samples required are MUCH more than a quick test will give you, especially
if you test engines that are really close. When you get a result of say 16-14
with an error interval of 10, you really can't say anything for sure.

One engine is better than the other, unless they are equal.  :-)


Bo Persson



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