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KGSRating Math/ Discussion
Sub-page of KGSRatingMath
rubilia: yoyoma, I have put some structure in the page. I hope that's ok to you. Probably the table headings aren't optimally worded for being headlines, but I didn't want to touch your text. yoyoma: Ah great, I thought about doing the same thing! :) Well I was dreading updating this with exponential decays when I suddenly realized you can make all these calculations using some simple calculus. Next to add: a section about the myth that if you win 55% of your even games you will promote. NOT TRUE!! BTW wms plans to add a "trend" feature to the rating system. This would attempt to see that someone is starting to win games at a high rate, and try to promote them faster. I didn't quite catch how he said it would work. Mef: Just a semantics issue - but wouldn't things like 2.9 and 2.5 be ratings and not ranks? I thought ranks were always the solid number, 2d. This may just be picking nits, but I like things to be clear. yoyoma: Yes. I made a little effort to be correct in that regard, but it wasn't my top concern. If you see any rank/rating mistakes please feel free to correct them. Probably just use rating everywhere would be easiest. I guess maybe the term "promote" is a little ambiguous there too because it implies rank... But maybe we can let that slide. :) Mef: Hehe, ok if I see a mistake I'll try to correct it. Now I'm curious about that winning percentage thing. Would if be different to win 4 games against 2.5's than to win 2 games against 2.9's and 2 games against 2.1's? Because if this is so, then it may still be possible to promote with a lower percentage. Perhaps you just need a >50% winning percentage at your own rating.
About "promoting": Maybe it would be helpful to specify (explicitely):
About the win ratio: The percentage of won games alone doesn't tell so much. If you, for an (admittedly, highly artificial) example, play 30% of your games against an effectively 5 ranks stronger player and win all of them, while losing the remaining 70% against effectively even opponents, you're supposed to get promoted rather quickly.
Concerning the introductional phrases: I can imagine it would be useful to apply the effective ratings paragraph to your tables, too. (Although it's not worded to be an introduction, yet.) It doesn't affect so much of your text - mainly the points 3 (which should be updated, btw), 4 and possibly 5. I am not sure about if you like that, because you might want to keep it as straightforward as possible. However, I think it can be done in a non-confusing way. For now, I'll put it up in the middle. yoyoma: I replied to a few examples people put; I'm sure that Mef and rubilia have a firm grasp on the math so this is more like violent agreement than anything else. :-) These "yes but what if..." cases are excluded from the tables in the simplifying assumptions section. I think we could add these examples to the main page by using footnotes to the assumptions section, which show the impact of that assumption (ie the one that assumes all games are against 2.5's -- average 2d's). Mef: Indeed, I completely agree with your numbers so far (can't say I've gone through as much work as you have and have completely double checked all of them, but I didn't see anything that looked wrong). In fact, I think that the numbers seem pretty logical, since one would expect a 3d to be able to beat the average 2d in at least %60 of their games, it would seem rather odd if only 51% were the necessary demonstration of skill for promotion. rubilia: I think, the tables could gain additional value if even a dumb first time reader understood that the main part of assumption no. 4 is, to play the games against average opponents of his/her rank, while the "average 2d" assumption is just an exemplary interpretation. etrynus Here is a question - say you have been playing with a -4.5 rank, and say that many months ago you played a game with an escaper at a handicapped rank of -10 (since you weren't as strong back then). Then, if the escaper escapes enough games so that you get credit for that win, can that somehow decrease your current rank?
Calvin: Maybe I'm missing it in the details, but where's the algorithm that gets that '?' to go away? It seems like I (user "ticktock") should have played enough rated games by now, but still I have the '?'. Could I be damaging my chances of getting a stable rating by accepting games from players with ranks that are too different?
This is a copy of the living page "KGSRating Math/ Discussion" at Sensei's Library. ![]() |