Re: Fw: [pbmserv-dev] ratings in multiplayer games

["David J Bush" <twixt@cstone.net>]

| > However, as has been pointed out, under the current
| > system, provisional players can lose rating points even
| > when they defeat HIGHER rated players. 
| 
| this is news to me....  I know a player provisional player could defeat a 
| lower ranked player and go down in rating, but I was not aware that a player 
| could beat a higher ranked player and go down in rating.  Are you certain 
| about this?

Sorry, I should have directed my initial post to pbmserv-dev.
But since you asked, here is a quote from
http://www.gamerz.net/pbmserv/ratings.html

"The rating during the provisional period is the average of a set of values,
one for each game played.  The values (of which the rating is an average)
depend on whether the opponent is provisional, or is established.  The value
against a provisional player is the average of the two ratings (using 1600 if
the player has never played) plus 200 times the outcome (which is -1, 0, 1
for loss, draw and win).   The value against an established player is the
opponent's rating plus 400 times the outcome.  Some extra points are now added
to the rating for the purpose of keeping the average rating of all established
active players close to 1720.  In particular, 1/5th of 1720 minus the current
average is added to the rating."

If your provisional rating is over 1720, this bias will subtract points
from your rating. So even if you beat a player rated the same as you,
you will lose points, particularly as you near the end of your 20 games,
when your average rating stays close to the same.

David