From: jhc@iris.uucp (James H. Coombs)
Subject: Re: 50 out of 100?
Reply-To: jhc@iris.UUCP (James H. Coombs)
Organization: IRIS - Brown University
Date: Thu, 16 Apr 1992 21:37:19 GMT

In article <1992Apr16.200104.14874@cis.uab.edu> sloan@cis.uab.edu (Kenneth Sloan) writes:
>In article <1992Apr16.180234.5960@cs.brown.edu> jhc@iris.UUCP (James H. Coombs) writes:
>>In article <0dv3YdT0BwxKIW7ohf@transarc.com> Ron_Kownacki@TRANSARC.COM writes:

>>Ok, so what did I miss?  The probability of 1 head out of one toss is
>>1/2.  What is the probability of 50 heads out of 100? 

Thanks for the several corrections that have been posted.  I was
confusing the probability of at least 1 head out of 100 with exactly 50
heads out of 100.  Two very different things, to be sure.

>Please.  Before you start proposing additions, corrections, and
>criticisms of the Elo system:

I am trying to understand the system.  I don't think I have proposed
any modifications; I certainly don't have anything better.

>    1) read and understand a book on probability ad statistics

I do this every 5 years or so, but it comes up so rarely that I
forget.  One thing that I think I retain is the importance of "in the
long run" in the application of statistics.  So, I was trying to get at
the idea that the rating system does not help us predict the outcome of
individual games.  Or, better, it tells us that A has a 1/4 chance of
beating B in the game they are about to start.  It does not mean that A
WILL lose to B. And it does not tell us that A WILL lose to B UNLESS A
plays in a special better-beater style.  Now there's an issue that I
have not seen in books.  What if A varies his behavior because of
knowledge of the probabilities?  Coins don't do that.

Anyway, just to try to express the fundamental idea clearly and
correctly.  If A has a 1/4 chance of beating B, we should not be
surprised at A's winning 1/1 or even 2/2.  This seems to me part of
learning tournament chess.  A should not be intimidated by 200 points,
nor should A get the big head about beating a player rated 800 points
higher.  One or two games does not tell us much.  This is a personal
lesson.  I won 3/4 in my third tournament and decided that I must
actually be a Class C player, but in my next tournament I won my
"normal" 0/4.

>    2) read Elo's book

Which is?  Is it really worth a read?  I feel that I have a novice's
understanding of the rating system to go along with my novice's
understanding of chess.  What will I get out of this book?

Another anecdote.  I won 1/2 point from 3 games with 1700-1800 players
last weekend.  I was close to a draw in one game I lost.  The last
player blew me off the board.  I tend to think of this last player as
much better than the other two, but then perhaps I just gave him the
right opportunity at the right time.  Next time, it may well be the
other way around: the drawer will drub me and the drubber will draw
me.  Still, my tendency is to think of the one as much better than the
other.  And, the weird thing is, I gave the drawer more opportunity
than I gave the drubber, perhaps I gave him so much opportunity that he
fell asleep for a moment.  (I sacced my e pawn to get out of serious
trouble, but in accepting my 3-move combination, he overlooked a
capture of my pawn on g2 and rook on h1.)  What does it all mean?  I
picked up some points, but otherwise I find no ratings significance in
this.  The real lesson is not to play b3 in order to oppose Bb2 against
his Bg7 and, in the process, to allow a pin of my Kc3 to my Ra1 or my
unprotected Bb2!  The deeper lesson for me is to think through the
tactics concretely for more than 2 moves.

Thanks.  --Jim
Newsgroups: rec.games.chess