Author: Ricardo Gibert
Date: 03:33:57 07/28/00
Go up one level in this thread
On July 28, 2000 at 02:12:50, Peter Kappler wrote:
>On July 28, 2000 at 01:23:55, Dann Corbit wrote:
>
>>On July 28, 2000 at 01:15:46, Peter Kappler wrote:
>>
>>>On July 28, 2000 at 00:50:09, Ratko V Tomic wrote:
>>>
>>>>Well, you're unjust to Thorsten. The rating calculations
>>>>extract very little data from each game, about 1.58 bits
>>>>per game (i.e. log2(3)). On the other hand, each ply contains
>>>>about 5-6 bits of data, or for a 100 ply game you have 500
>>>>bits of data produced. Hence the conventional rating tests
>>>>based on the 3-way game result are very highly inefficient,
>>>>they keep about 0.3 percent of info produced in game.
>>>
>>>Why 5-6 bits per ply? Just enough to represent an appoximate evaluation of the
>>>position?
>>>
>>>>
>>>>The advantage of ratings to the more efficient information
>>>>extractors (such as human brain) is that one can compute
>>>>such rating without even knowing how to play chess. Another
>>>>advantage is that they're not biased by human subjective judgment
>>>>(the ratings may manifest other biases which reduce their
>>>>predictive power, especially when extrapolating to a new opponent
>>>>from a small number of earlier opponents). A human chess player
>>>>likely extracts 100 times more info per game than the mechanical
>>>>rating calculator, and the stronger the player the more info he
>>>>can extract.
>>>>
>>><snip>
>>>
>>>
>>>Well said. I have always felt this way, and seeing the idea explained so
>>>eloquently is comforting in a strange way. :)
>>
>>I don't believe it for a minute.
>>
>>I have seen too many times when someone is completely wrong in their assessments
>>to fall for it.
>
>
>What he says makes more sense if you assume a strong player is making the
>assessments.
>
>I'd venture that a GM can estimate a player's rating to within +/- 200 points by
>just analyzing one game. I think the success rate would be at least 80%.
>
No. I'm over 2200 USCF and I don't think this is a good way to estimate a
players ability. There are several reasons why I think this. Some based on
practical experience and some based on my understanding of statistics.
I remember playing an A-player in a tournament and I he was able to create an
incredible amount of pressure in the middlegame. He kept finding incredible
moves I thought no A-player could find. I was barely able to survive and had
come to the conclusion he was way under-rated and that a draw would be a good
result for me, despite the rating differential.
I made it to an endgame with meager chances to draw. That was when the "strong
player" vanished and he started to play like a C-player. He didn't blow the game
in one move. He made a series of weak moves to blow the game and I wound up
winning!
He was 2400 strength in the _particular_ middlegame we played, but only 1500
strength in the endgame. This was a player with _big_ holes in his make-up as a
player. A lot of strong players would have folded up in the middlegame and come
away with the impression this guy was super strong.
Another possibility is a different kind of middlegame (a closed position) would
have revealed his weaknesses as a player. It all depends on the player.
>And if you gave him 4 or 5 games to analyze, I'd probably have more faith in the
>GM's estimate than the player's actual rating. :)
>
No. It is even possible in 4 or 5 games that a player is able to get positions
that complement his playing style and he looks like he can do no wrong. There is
no substitute for an objective assessment using a large number games against a
_variety_ of players.
A friend of mine, about 2100 strength had a record of 5-0 (slow OTB tournament
play) against IM Kamran Shirazi (2550-2600 strngth). Their respective styles
were such that he would beat the crap out of him in every game. Luck had nothing
to do wih it. In a sixth game, he was crushing him also, but his habitual time
trouble allowed Shirazi to limp away with a draw. My friend was not a very good
blitz player and spoiled a lot of games in the move 30-40 range.
I think you must conclude that 4-5 games are not enough or my friend is as
strong as Kasparov. Which is it?
Chess playing programs can be similar. The respective opening books can slant
the outcome greatly in one direction or the other. Using the same opening book
does not help, since the types of positions resulting may be limited and slant
things greatly in favor of one program.
To determine strength accurately, a player, computer or human, needs to be
tested against a random sample from a _population_ of players. This is what a
book on statistics will tell you.
Believe it or not, a World Championship match does _not_ determine who is the
strongest player. Their ratings do! A match _only_ determines which player is
able to "dominate" the other player. The result may be contrary to the actual
strength of the players. It does _not_ matter how long the match is.
-Rick
>
>--Peter
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