Forum Archive : Ratings

Why high ratings for one-point matches?

From:   David Montgomery
Address:   monty@cs.umd.edu
Date:   12 September 1995
Subject:   Re: One point matches
Forum:   rec.games.backgammon
Google:   434lg6$56b@twix.cs.umd.edu

Walter Trice writes:
> I've been puzzled by the fact that individuals have achieved
> unusually high ratings on FIBS by limiting themselves to
> one point matches.  WHAT IF it is intrinsically more difficult
> to play one point matches than to play games in which gammons count?

I keep track of my FIBS results at different match
lengths versus players of different strengths, and I
have a little program that will iterate my results,
updating my rating, until it converges.  My iterated
rating for one point matches has always converged to
over 2000.

I'm not sure why this is so.  My iterated rating over
all matches has consistently averaged 1800-1825.  This
difference is consistent with many hypotheses, namely:

0) I haven't gathered enough data.
1) My match strategy and cube handling skills are very weak.
   (In light of your hypothesis I realize I should add:
    my gammon handling skills are very weak.)
2) I play better relative to my opponents in the endgame
   relative to the opening.
3) The rating formula does not work well for large rating
   differences.  (More of my one point matches are against
   weaker players, for a variety of reasons.)
4) The rating formula underestimates the skill present in
   one point matches.

Your hypothesis that one point matches might be intrinsically
more difficult than games with gammons technically would
not explain the high ratings of one point match players,
since if the rating formula accounted appropriately for
the skill in one point matches (whether or not they are
more difficult than games with gammons), then higher
ratings would not result.   Presumably you are also
hypothesizing that 4) is true too.

My own belief has always been that 0) was a distinct
possibility, that 1) was probably true, but probably not to
the tune of 200-300 rating points, that 2) was relatively
insignificant, that 3) contributed but probably by less than
50 points (I base this on looking at my ratings iterated
separately against weaker players and stronger players),
and that 4) was the most likely candidate.  With the advent
of one_pointer, loner and mloner I am more convinced than ever
that 4) is true.

With respect to the reasons that one point matches might
have more skill than you would expect, my intuition is that
the primary reason is that the games last longer.  Although
cube decisions are more difficult than checker play decisions,
when you add an average of 25 extra checker plays, the
cumulative effect may be more important than one or two
primary cube decisions.

David Montgomery
monty on FIBS
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Constructing a ratings system  (Matti Rinta-Nikkola, Dec 1998) 
Converting to points-per-game  (David Montgomery, Aug 1998)  [Recommended reading]
Cube error rates  (Joe Russell+, July 2009)  [Long message]
Different length matches  (Jim Williams+, Oct 1998) 
Different length matches  (Tom Keith, May 1998)  [Recommended reading]
ELO system  (seeker, Nov 1995) 
Effect of droppers on ratings  (Gary Wong+, Feb 1998) 
Emperical analysis  (Gary Wong, Oct 1998) 
Error rates  (David Levy, July 2009) 
Experience required for accurate rating  (Jon Brown+, Nov 2002) 
FIBS rating distribution  (Gary Wong, Nov 2000) 
FIBS rating formula  (Patti Beadles, Dec 2003) 
FIBS vs. GamesGrid ratings  (Raccoon+, Mar 2006)  [GammOnLine forum]
Fastest way to improve your rating  (Backgammon Man+, May 2004) 
Field size and ratings spread  (Daniel Murphy+, June 2000)  [Long message]
Improving the rating system  (Matti Rinta-Nikkola, Nov 2000)  [Long message]
KG rating list  (Daniel Murphy, Feb 2006)  [GammOnLine forum]
KG rating list  (Tapio Palmroth, Oct 2002) 
MSN Zone ratings flaw  (Hank Youngerman, May 2004) 
No limit to ratings  (David desJardins+, Dec 1998) 
On different sites  (Bob Newell+, Apr 2004) 
Opponent's strength  (William Hill+, Apr 1998) 
Possible adjustments  (Christopher Yep+, Oct 1998) 
Rating versus error rate  (Douglas Zare, July 2006)  [GammOnLine forum]
Ratings and rankings  (Chuck Bower, Dec 1997)  [Long message]
Ratings and rankings  (Jim Wallace, Nov 1997) 
Ratings on Gamesgrid  (Gregg Cattanach, Dec 2001) 
Ratings variation  (Kevin Bastian+, Feb 1999) 
Ratings variation  (FLMaster39+, Aug 1997) 
Ratings variation  (Ed Rybak+, Sept 1994) 
Strange behavior with large rating difference  (Ron Karr, May 1996) 
Table of ratings changes  (Patti Beadles, Aug 1994) 
Table of win rates  (William C. Bitting, Aug 1995) 
Unbounded rating theorem  (David desJardins+, Dec 1998) 
What are rating points?  (Lou Poppler, Apr 1995) 
Why high ratings for one-point matches?  (David Montgomery, Sept 1995) 

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