GameKnot related: rating system
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evader23
08-Feb-13, 04:21

rating system
How did I lose 18 points to someone only rated 300 points below me. Yes I should have one not the point here.

The way I understand the rating system it is the standard elo system with a fixed k factor of 20. Given that the elo system has a rating range of 800(correct me of i'm wrong there) shouldn't I have lost like only 300

Ok even rating on a lose you lose 10
lose to 400 below you you should lose 15
lose to 800 you should lose 20
or am I over simplifying it.

Even you you take my higest on his lowet rating during the match we were only 400 apart

Again consfused

Yes I am been in a slump latley and should be thinking more before I move yadda yadda yadda

But if someone on here could explain the rating system better I'd appreciate it
tactical_abyss
02-Mar-13, 20:22

You lost 18 points?I looked on your past games several pages back and did not find a loss of 18 points.Point the game out to me,i'm interested.Is it in a ladder game?
garos
03-Mar-13, 00:18

TA
I'd say the one that finished against player 'lady' on the 7th of Feb.
garos
03-Mar-13, 00:46

According to the which Past Games figures you use (evader23 or lady) the difference in rating is either something like 308 or 349. If I were to play someone approximately 350 below my rating, it clearly states that a loss would cost me almost 18 points. So, it seems about right to me.

It appears that 20 rating points is the maximum you can lose or win. I'd lose 19.9 against the last player on GK's list and only get 19.7 for a win against TA.
algol
03-Mar-13, 02:15

evader23
When I look at your game against lady, it gives your rating as 1195 and hers as 815. Her rating when the game ends is higher, 838. The rating difference is approximately 357 rating points.

If the lower rated player wins, the rating delta will be 20 / (1+10^(-357/400)) = 20 / 1.128 = 17.7. This formula is referenced in GK's FAQ.

If the rating difference were 359, the calculated delta would be 17.8, which is the stated one for this game. So the small discrepancy must come from the fact that we do not know the rating of the players accurately enough.

One would get a 15 point rating exchange when 15 = 20 / (1+10^(-R/400)) or for a rating difference between the players of R = -400 * log10((20/15)-1) = 191.

The formula does indeed give a delta of 10 rating points for a win against an opponent with the same rating (R=0). And for R=800, the delta is 19.8, i.e. very close to the 20 you expected.
tactical_abyss
03-Mar-13, 05:05

Yes garos,
I missed that one with lady.And algol,correct.Evaders rating numbers seem to add up correctly.

Let me add:
If I were to lose against a 2152 player which is 359 points below my rating of 2511,then I would lose 17.7 points.It would also COST me a -7.7 points for a draw!So for me,just playing a 2100+ player in a rated game is technically disadvantageous and illogical...atleast for me!The cards are more in a 2100+players favor than mine,if you understand what I mean.The 2 points for a win against a 2100+ player aren't even worth it,and not worth the "risk"...atleast not in my book.Thats why you will see many of the smarter 2300-2600 players keeping a strict automatic challenge decline rule for all incoming challengers.Before I did that,I was getting a ton of players more than a 1000 points below my rating challenging me.And a win would yield me a "zero"against those players and a draw(even by remote possibility)would cost me a ton of points.And a loss against a player a 1000 points below me....I don't even want to fathom it...it makes me shake more than consuming 20 big cups of espresso!Ha Ha!Now,they see they can't challenge so they still message me pleading for a game...but I respectfully decline.Except for an occassional unrated game,then no problemo.I'll play a class "J"player unrated.(thats someone with a rating 199 and BELOW).But I think the lowest on this site is like 391,so i'm out of luck!
evader23
03-Mar-13, 05:47

Ok I get it now I just thought it strange to lose 18 points to someone 300 points below me when if I'd lose to 800 points below me I'd only lose 20 but it sort of makes sense now. The formula is a little more comple than a simple sliding scale so thank you everyone