posted by Dr Feelgood (Dr Feelgood) on 06/05 at 18:19
I've had a discussion with a few other players about the Elo rating system. Seems none of us can figure out just how it works. I've been able to figure it has to do with win-loss ratio AND number of games played. But just can't figure out the specifics. Anyone have this pegged and want to share the secret of how it works??
It's mostly about the odds of a specific player winning over another specific player, given their current ratings. If Maria has a higher rating than Nitin, the odds are that Maria will win. If it's just a small difference in ratings, those odds might just be 55%/45%, but if it's a big difference they can be much higher, say 75%/25%. Let's take the 75%/25% situation: The odds are very much in Maria's favor. If Maria does actually win, the system increases her rating by a small amount (the amount is calculated using the inverse of the odds of her winning) and decreases Nitin's by a small amount. It's only a small amount because the result was in line with expectations, and so the relative ratings must be mostly correct. If Nitin wins, though, the system increases his rating by a larger amount and decreases Maria's rating by a larger amount -- because the result suggests that their ratings should be closer together than they are.
When the system is just getting to know a player, it uses larger adjustments to try to get that player to the right general area faster (this is the "learning period", called the K-factor).
The number of games you've played only affects your rating positively if you win more than you lose. Say two better-than-average players arrive, Kalil and Joe, and they happen to be exactly as good as one another. If Kalil plays 200 games with an average set of players and Joe plays only 50 with an average set of players, Kalil's rating will be higher than Joe's because he's won more often, even though they're exactly as good as one another. Similarly, though, if both were less-than-average players and played those games, Kalil's rating would be lower than Joe's because he'd lost more games, again despite the fact they're exactly matched. So the number of games you play does come into it a bit.
posted by Dr Feelgood (Dr Feelgood) on 06/06 at 16:23
Thanks for the information, T.J.!
I googled and ended up with information overload and a bad headache. I now have a much better understanding and appreciate my Elo rating more! Gotta beat those really good players!
Thanks again for taking the time to clarify!!
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