Beginner Questions:: Ratings

[MikeCPharmD]

I had a couple of general questions about something people seem to take for granted: Ratings:
1) How are ratings calculated?

2) When results of tournaments are displayed, there are +/- numbers after the players' rating. What is the significance of these numbers? (Looking at Ebutaljib's post on the history in the 2008 Championships, the +/- was about 2% of their ratings--The 2007 matches in Elista, Russia showed Gata Kamsky and Etienne Bacrot showed that +/- number more 12% of their ratings at the time.)

3) How quickly and to what degree do ratings change? (Again, by looking at Ebutaljib's post in history, if I look at the results from Elista, Russia, Levon Aronian was at 2759 during the qualifiers but in the actual World Championship he was 2750. Boris Gelfand remained at 2733 throughout. Alexander Grischuk was at 2717 in the beginning, but despite only getting 5.5/14 in the Championship tournament, he went up to 2726.)

Thank you in advance!

[MikeCPharmD]

I had a couple of general questions about something people seem to take for granted: Ratings:
1) How are ratings calculated?

2) When results of tournaments are displayed, there are +/- numbers after the players' rating. What is the significance of these numbers? (Looking at Ebutaljib's post on the history in the 2008 Championships, the +/- was about 2% of their ratings--The 2007 matches in Elista, Russia showed Gata Kamsky and Etienne Bacrot showed that +/- number more 12% of their ratings at the time.)

3) How quickly and to what degree do ratings change? (Again, by looking at Ebutaljib's post in history, if I look at the results from Elista, Russia, Levon Aronian was at 2759 during the qualifiers but in the actual World Championship he was 2750. Boris Gelfand remained at 2733 throughout. Alexander Grischuk was at 2717 in the beginning, but despite only getting 5.5/14 in the Championship tournament, he went up to 2726.)

Thank you in advance!

[KHollister]

Look at the Chessmaster Grandmaster Edition FAQ (http://forums.ubi.com/eve/forums/a/tpc/f/4221052685/m/3211095046)... it will explain how the ratings are calculated. http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

Ebutaljib will have to explain the +/- numbers in the crosstable... I'm afraid I don't know. http://forums.ubi.com/images/smilies/blush.gif

As to how quickly ratings change... your rating will change every time you play a rated game. However, keep in mind that in professional chess, the "official" list of ratings is published by FIDE four times a year, so someone's rating might actually be higher (or lower) than the currently published rating.

[ebutaljib]

1) Which ratings do you mean? Ratings in Chessmaster (in that case follow the link that KHollister gave) or official ratings published by FIDE - World Chess Organization?

You can read about FIDE ratings (ELO) here (http://www.fide.com/component/handbook/?id=73&view=article). It isn't quite that complicated as it looks http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif


2) Those numbers represent rating performance in that particular tournament. Let's look at the table of recently finished Karpov tournament in Poikovsky:
http://www.pgndownloads.com/files/2009/2009_Poikovsky.png
First column is the players rating. Second column says how well or poor does the player performs in this tournament compared to his rating. For example Motylev performance in this tournament was 2677+237=2914, which means that a player with a 2914 rating was expected to score 7 out of 9 in this tournament, like Motylev did. Shirov performance was 2745-273=2472, meaning that he performed like you would expect from a 2472 rated player (and not from a 2745 rated one http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif)

3) Official FIDE ratings list is published every 3 months (January 1st, April 1st, July 1st, October 1st) so thats how often the official players rating can change. There is an unofficial live rating (http://chess.liverating.org/) list, where the ratings are calculated daily. For example, Motylev's official rating is still 2677, but due to his recent good results (especially in the above mentioned tournament) his "live rating" is already 2709.6, meaning that in the next rating list (published in few days on July 1st) his rating will be 2710 (rounded to integer).

"live list" always represents players rating if the ratings list would be published on that day.

P.S.: Before year 2000 I think, official ratings list were published only twice a year, and further in the past only at yearly intervals.

[MikeCPharmD]

Thank you Ebutaljib. You answered my questions perfectly and it makes more sense now. Thanks!