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Subject: Re: Statistical data about draws and rating differences

Author: Andrew Dados

Date: 07:13:01 02/05/01

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On February 05, 2001 at 09:49:27, Günther Simon wrote:

>On February 04, 2001 at 13:58:11, Andrew Dados wrote:
>
>>
>>I decided to find out 'true chance' of draw outcome from real games.
>>The below is summarized output from my twic game files.
>>Rdiff means difference of players ratings in the (range, range+25).
>>Integrestingly around range of 0 draws approaches 50% and better won about 25%.
>>
>>Now if you take 2 tosses of coin you'll get total score of 2 heads in 25%, 1
>>head in 50% and 0 heads in 25%...
>>
>>
>> files: 176      games: 170464   decisive (counted) : 128803
>>
>>Rdiff+  games   %draws  %better won
>>=======================================
>>0       14480   48.82   25.67
>>25      15365   46.57   31.45
>>50      15784   44.60   35.52
>>75      15429   41.80   39.62
>>100     14092   38.68   44.26
>>125     12121   35.08   49.18
>>150     9926    31.92   54.47
>>175     8129    28.34   58.89
>>200     6478    25.39   63.71
>>225     4707    22.82   67.94
>>250     3443    20.65   69.82
>>275     2575    18.45   73.67
>>300     1879    15.59   77.38
>>325     1370    15.62   78.83
>>350     970     10.52   85.46
>>375     687     9.32    86.90
>>400     453     7.06    89.18
>>
>>Is one chess game statistically equivalent of 2 coin tosses? :)
>>
>>-Andrew-
>
>There is something in this statistics which makes me get headaches
>because it has not much to do with chess.
>The point is in the mass of draws "played" in just a few moves sometimes
>even in zero moves!! There are several reasons for this behaviour like
>knowing the opponent very well,sharing at least prices,being exhausted
>after a long tournament and some others...
>But will this games not going to falsify the statistics?!
>I presume that in all kind of huge collections of chessgames nowadays are
>a terribly lot of such "games".(For my original Bigbase of CB I know this)
>For myself I decided long time ago to delete all drawn games under move 9
>or 10 in my database well knowing that this is just kind of difficult
>compromise.
>But the question is how can I trust the statistics e.g. in showing the
>winning percentage of different opening variations or cant I trust
>statistics of that kind anyway?

You have a point here indeed. For me however the question is not really
'exactness' of game scores, but 'trend'.

I am curious how can I include draws in statistical modelling to get them close
to reality. No matter how I do it I get much higher 'confidence' then without
them (See Bruces concerns in '60-40' thread somewhere below). I am becoming
convinced that just existence of 3-state score raises confidence of performance
ratings above usually applied 'win-loss' model.

-Andrew-



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