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How does the rating system really work?
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How does the rating system really work?
Posted in 
How does the rating system really work?
I noticed that the rating system does not work as written in FAQ (
 In particular, the number of won stones and the number of ends in the match affect the rating. Although this is contrary to the rules and the essence of the game.
So what formula should I use to calculate the ratinge change?
Hi, I usually play 6 enders  & there’s a certain player who always says to me “What’s my rating going to be if I win”?   I go to the faq, put it in as a 6 ender & put in any winning score, e.g 5-4. I then reverse it & put in 4-5 & tell him what his rating will be win or lose & it’s always been accurate. It’s never let me down yet.
Ok. I played last match of 2 ends (there's no important for rating system, only number of games an it's 1 game). My rating was 247 before the match and opponent's rating was 387. So I go to the faq and calculate:

the difference in ratings - dr=247-387=-140
ecpected score - We=1/[10^(-(-140)/400)+1]=0.309

I played the match in a draw, so real score is W=0.5 for me and 0.5 for my opponent (the exact match score isn't important, only "win" or "lose"). The sum of the scores is n=0.5+0.5=1. I calculated my rating change by faq:


But my rating was 250 after the match and real rating change is +3, not +6. Why?
Hi, there are two ways to go about rating calculations. Ever since the rating system switched a few years ago it's different (better in my opinion) than it was.

Option #1: As you see in your match history it is always recorded as one game, with the result being a win or loss (+ or -) with the number of ends (2, 4, 6, 8, 10) AS LONG AS the original number of ends was set. This does not apply for the *ANY* amount of set ends feature. For the rating calculator, enter the game as a one-end match, with the final score being as shown in the info. So, if I am rated 400 playing another 400-rated player, and I win a 6-end game 7-4, I enter the result as +6 (win, followed by number of ends) for me and 0 for the opponent. My rating increases to 422, and the opponent drops to 378.

Option #2: Enter the ratings as normal, but this time indicate the actual number of ends being played in the game (6 ends). Enter the actual score of the game. The rating result will be the exact same, changing to 422 and 378.

As for the actual design of the rating system, you can read more about Árpád Élő's rating system here.