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Subject: Re: Small number statistics and small differences

Author: Peter Fendrich

Date: 11:23:28 08/14/98

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On August 14, 1998 at 11:36:56, Dan Homan wrote:

>On August 14, 1998 at 10:42:04, Bruce Moreland wrote:
>
>>
>>On August 14, 1998 at 06:08:36, Dan Homan wrote:
>>
>>>On August 12, 1998 at 09:15:19, Bruce Moreland wrote:
>>>
>>>>
>>>>On August 11, 1998 at 06:52:02, Tony Hedlund wrote:
>>>>
>>>>>
>>>>>>So I think 4-0 actually turns out to be a significant result.  If you score 4-0,
>>>>>>you can say that there is a very good chance that the one with the wins is
>>>>>>better than the ones with the losses.
>>>>>>
>>>>>>You can't say this if you pick out a string of 4 wins in a row in the midst of a
>>>>>>longer match, since you might be selecting a fluke case, but if you just start
>>>>>>from scratch, and get 4-0, you should be able to stop.  In fact I think you
>>>>>>might be able to stop if you get 3.5 - 0.5, but I am less certain of this case.
>>>>>>Someone who has more statistics than I may be willing to comment on this.
>>>>>
>>>>>Recently I played the match Shredder2 P200 MMX 64MB - Rebel8 P90 16MB.
>>>>>Rebel won the first four games but Shredder won the match with 11-9.
>>>>
>>>>That shouldn't happen very often.
>>>>
>>>>bruce
>>
>>If this does happen more often than it should, perhaps some effort could be
>>expended to figure out why.  I don't know why it would happen more often than it
>>should.
>>
>>>The problem with small number statistics is that they can be very
>>>mis-leading.  A 4-0 result in a 4 game match between nearly equal
>>>programs (with 20% draw chances) happens about 1/40 th of the time.
>>>A 3.5-0.5 (or better) result happens about 1/13 th of a time.
>>
>>If you want to be able to say, "program A is stronger than program B, by at
>>least a little bit", would you rather have a 4-0 result or a 105-95 result?
>>
>>You should get a bogus result from 4-0 only 2.5% of the time by your
>>calculation,
>
>Actually I think my calculation was wrong.  I didn't consider the chance
>of the weaker program going 4-0.... see below.
>
>>how much do you want to bet that you'd get a bogus result from
>>105-95 a lot more of the time?
>
>Of course, but my point is that if you think you are learning anything
>useful from 4-0 result in a 4 game match between top programs you are
>wrong.  I initially thought this was a great idea until I thought about
>it - the more I think about it the worse it gets.

I don't understand how you guys get these results. In my world probability is
completely different from confidence. If the probability is odds, chance or
whatever, the confidence is a meassurement of how sure we can be of the
probability value itself. The information given by a 200-game match gives far
more confident probabilities than a 4-game match. In the 4-game match it's not
even applicable to use the term confidence. It's as worthless to compute like
meassuring 1/100 of a seconds with you wrist-watch.

//Peter



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