Forum Archive : Miscellaneous

How bots rate you

From:   Phil Simborg
Address:   psimborg@sbcglobal.net
Date:   2 March 2010
Subject:   Understanding the Bots
Forum:   bgonline

> One thing I have always found with bot analysis is that, if you play OK
> in a game where you have a series of very tough decisions, you'll end up
> with a low rating. Conversely, you can be awarded world champ status in a
> game where you've basically had nothing to do.
> I understand why this happens and obviously the error analysis should be
> absolute, at least if it is to be used as a performance measure over a
> variety of games. But I was wondering if there had been any attempts to
> measure the difficulty of backgammon decisions? It would be useful to
> have some sort of rough stat for a game, indicating the 'tarriff', if you
> like.

To my knowledge, there is no way to determine how difficult a given play is
other than seeing how many humans miss the play and how many good players
have trouble with a given play. So the bot cannot know this. I guess it is
logical to assume that the worse one's PR or Elo, the more tough plays
there were.

You are absolutely correct that generally, the worse you played a given
game, the more likely it is that you simply had more difficult decisions to
make that game. That explains why I might have a PR of 0.0 one game and
11.0 the next.

As for whether some players do better with tougher decisions, that's pretty
much a self-cancelling, or oxymoron statement, because the better they do
the easier it was FOR THEM. The point is that no matter what your level of
play, everyone has their own demons as far as what is tough and what is

A very good example is a 15 question quiz that Falafel gave in Istanbul
last weekend. I got a copy and I missed 5 of the questions. Matt Cohn-
Geier, one of the best players in the world, missed 4, and Joe Russell,
another one of the best players in the world, missed 3, as did Kit Woolsey.
The interesting thing is there was only 1 question that all three of us
missed, and the rest were scattered. So even though these three players are
far better than I, there were some I got right that they missed.

Lucky guess could be one reason; the quiz factor could be another; or
simply different knowledge and skill traits could be the answer. Also note
that with them missing 3 and 4 and me 5, it would appear our skill levels
are close, but overall, they probably have an average PR rating 3 or 4
points lower than mine...so the other factor could be that a 15 question
quiz is simply not a long enough sample from which to draw any meaningful

So the answer is that you have to use a very large sample and not get hung
up on how you rate in a single match or game, and you really have to
compare apples to apples to see differences in skill.
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