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Old 11-30-2012, 01:07 PM   #22
Join Date: Jul 2009
Posts: 977

Originally Posted by beernutz View Post
I don't think NTRP is entirely based on ELO since ELO only considers win/loss/tie and doesn't use any type of game differential like number of moves whereas NTRP is just the opposite. I don't think most people here who have issues with the NTRP are arguing that it should not incorporate score and dynamic rating differentials into the formula but that it should also incorporate win/loss into it. Hybrid systems which use both exist so it is not beyond the realm of possibility to think that the USTA could also include it.
you are almost right. however the principle of the Elo system is not necessarily just win/loss/tie - it is the concept of 'expected result' and the notion of the weight of the match (sort of how important the match is). You can make this 'expected result' to be anything that makes sense for particular competition. in chess, as you correctly pointed out, it is win/loss/tie. In soccer (FIFA) it is win/loss/tie by a specific number of goals, and matches at World Cup have obviously more meaning than a friendly warm up match. In Canada Rogers rating for junior tennis it is only strictly win/loss, weighted depending on the rank of the tournament. In USTA apparently it was decided that it makes more sense to make an 'expected result' to be a particular game difference during the match.
I agree that including win/loss into formula would make sense. Although it can be easily argued that it already sort of is - in the majority of results, when you win more games, you win a match. I would not be surprised if USTA algorithm does take win/loss into account, in addition to pure game differential. But even if it doesn't, on average, using just game differential is good enough. Gaming the system is equally easy either way - so that discussion does not belong here.

I get the impression that most folks that bring up those edge cases where "a player such and such went 11:0 and he is not bumped. Another went just 5:6 and he got bumped" just need to realize that above all the level of competition is what really counts. If a player goes 11:0, with the average score of 6:1 6:1, but all of his opponents are at the very bottom of a given range, or perhaps some of them even playing up - that is not that significant of an achievement. It just does not show that a player is bump-up-worthy. And that is precisely what the ranking algorithm provides - a more objective picture of one's level, rather than looking at win/loss ratio only.
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