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Subject: Re: Statistics, computer evaluations and some trends

Author: Dan Andersson

Date: 08:47:31 11/19/05

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On November 19, 2005 at 10:00:31, Albert Silver wrote:

>On November 19, 2005 at 06:12:50, JNoomen wrote:
>
>>Thanks for all your comments on my Fruit-Diep report. At least it has given me
>>some ideas for a new posting, which is given below. I want to discuss 4 topics I
>>wanted to write about already for some time, but I never took the time do so.
>>Now your reactions gave me the necessary 'boost' to sit down and write down the
>>stuff.
>>
>>Statistics
>>--------------
>>In many database programs and chess computer GUI's there is the nice option that
>>it will tell you the exact statistics of the moves being played in a position,
>>as well as the average Elo of the players that played the moves. This gives
>>insight in how often a move was played, what it's success rate is and what type
>>of players (strong, less strong) chose the moves. When building a book such
>>statistics are very helpful and they can point you towards the best move in a
>>position. When building a book with f.e. the ChessBase GUI, using 200.000 GM
>>games over 2500 Elo, you already have quite a decent book.
>>
>>Still there are some topics that one should be well aware about:
>>
>>1. The game statistics are between humans and not between chess programs.
>>2. The score of a game (0-1, 1-0 or draw) says nothing about the actual
>>evaluation of a move.
>>3. Between the opening moves and the final result there is a complete game to
>>watch, with its ups and downs, its mistakes and brilliant moves and even
>>blunders.
>>4. A score of 25% for a move in a certain position never means that the move
>>should be bad. In fact it can be the only move or the best move available.
>>5. When using games only, you have no moves that will punish bad lines, or
>>defend against unsound attacks. Because such lines are never played between
>>strong players.
>
>Yes, this is clear. It is much like a sharp and previously successful line that
>is refuted. You could have it scoring 80% over the course of 100 games, and then
>one game reveals an indisputable refutation making the line more or less
>unplayable.
>
>Statistically it will still say 79% in favor of the unplayable move, and if you
>only look at the stats, you will not know this.
>

 From a mathematical standpoint expecting a simple statistical mean to yield the
value a directed acyclic graph is worthless. Mini-maxing of some sort will give
a better value as well as a critical path.

MvH Dan Andersson



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