Ladder Rating Bug [SOLVED]

[SilverKronos]

hi,

i played a game 2 days ago agains a player with 400 rating (not enough game to be accurate) on setons.
I was 1565 and i won ( it was hard ^^)
After that game, i relaunch a ladder game but my rating instead of growing up was lower (1563) than the previous game, which i won (1565).
In other words, i lost rating in winning a game ...

Anybody heard of this bug ?


ps: it's the first time i see this and it's not catastrophic, i only lost 2 point but it will be good to understand how this bug could happen

[ZLO_RD]

you can loose rating if you win game, only if your rating is much higher than opponent's rating

[SilverKronos]

Oooh so it's totally normal.

It's weird though

Thanks for your answer

[Vee]

It happens because of 2 things:

1. The rating actually consists of 2 numbers: mean and deviation. The rating that is displayed is mean - 2*deviation.
2. After every game, depending on the rating of your enemy, your mean and deviation get updated. However, also after every game your deviation gets increased a little bit to make sure that your deviation does not become 0 over time.

If you play against a very low rated player who has a high deviation, then after you win your mean goes up a little bit, and you deviation goes down a little bit, but because of that standard decrease in deviation after every game your displayed rating actually goes down. Don't worry though, because your mean rating increased a little bit. You actually gained rating from that game if you look at the long term, because long term your deviation will go down again.

tl;dr: it's just because of how rating is displayed, actually your rating went up a very small amount.

[Deering]

It will be due to your deviation rising more than your mean rating. The shown rating is your mean - 3*deviation. So say your mean went up 1 point for winning, but your deviation also went up 1 point. Your shown rating will be 2 points lower than previously. The result is your rating curve (its not just a single number) moves to the right but becomes flatter.

ninjad

[SilverKronos]

Thanks Vee and Deering,

Now i understand, i was "worried" for nothing ^^

Problem Solved