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Old 11-30-2012, 10:44 AM   #18
Join Date: Jul 2009
Posts: 787

Originally Posted by jmnk View Post
Let's see. Assuming you play in 4.0 league, so you are going to play only 4.0 NTPR players (in fact, due to the fact people are allowed to play up, you may in fact play someone below 4.0, but --never-- above 4.0). Again assuming that all 4.0 players are uniformly distributed - i.e there's equal chance of your opponent having 3.52 dynamic ranking as someone having 3.97 (in short, meeting a player of any dynamic rating in 3.50-3.99 range is equally likely). If you ranking is 3.89, you have 78% chance of meeting someone with a lower dynamic ranking. ((3.89-3.5)/0.5). The chance of that happening 15 times in a row is actually ~0.024 - which is a bit over 2%. Not sure where you got your "less than 3 one thousanths of one percent." from??
Note, that both of the above assumptions made the result --smaller-- that what would have happened in real life. Since you actually --can-- play someone with DR less than 3.5, and in any range there are likely more players in the lower/mid part of the range than in the upper range - so again in reality you are more likely to meet someone with a lower ranking.

I do not scoff at the idea of using W/L record as being meaningful. I'm sorry if it appears so. I'm saying that using games difference for casual USTA play is 'more meaningful' than using just W/L results.

Because top PROs play around 75-100 matches a year so there's way more data sample with just W/L ratio. Those that lose early have only 30-50 matches, the data sample is small, that's why it can be easily argued that PROs in 150 - 300 range are pretty much all the same level and they move so much with each result. Look at Janowicz - he had essentially one excellent week and few so-so results, and he moved from outside 100 to 26 spot. While I like him a lot - you really think he improved so much?
In addition in ATP tournaments, the points you get depend on the round you won. You know why - because underlying assumption is that the deeper you advance the better players you meet, so your win is worth more. Of course it does not work all the time - but on average, over the course of the year, it works fine.
But that will not work for USTA league - because players simple do not play that much. And there's no 'going deeper' in the tournament, for those that do not advance to post-season play (which is a vast majority) all the matches are worth the same.

Again - please propose a system and we can take records of few players from USTA and I'm sure we will be able to show you that your system is equally, if not more, illogical.
Originally Posted by LuckyR View Post
Perhaps you are unfamiliar with the term "sandbagger". I guess it is unknown in your league. Over here on planet Earth, folks are familiar with it.
not sure what sandbagging has to do with this discussion. Are you suggesting that one cannot sandbag by outright losing the match rather than winning it closely? Could you kindly clarify what your point is?

Originally Posted by LuckyR View Post
My numbers were assuming that someone with a slightly above halfway rating in the division (your example of 3.89) would likely have a 50:50 chance of playing someone worse rather than better (regardless of their "rating"). As you know .50 to the 15th is 3 to the -5th.
I'm not sure why you think that 3.89 DR is 'slightly above' halfway ranking? Halfway is 3.75. 3.89 is way more that slightly above halfway. Also, next time you make an assumption that is not obvious to anyone but you yourself, please make it clear. Rather than, you know, implying that someone else does not know what 0.5^15 is.
But if you want to discuss a case where someone is indeed at the halfway point, at 3.75. in this case he needs to get his ranking up by .25 points to get bumped. It is significantly harder to earn this .25 dynamic ranking points. Someone who started at 3.89 needs only .11 to get bumped. It really all evens out - you start at the higher DR, you need to play better opponents to move your DR up, but you only need to move up by a small amount. You start at lower DR - it is easier to earn DR points (because you are more likely to meet higher ranked opponents more often) but you need to earn more of those DR points. the system actually makes it all take into consideration which makes it, I don't know, logical?

Originally Posted by LuckyR View Post
The USTA knows that their system is flawed by allowing sandbagging, hence their decision to preempt criticism of it by stating that 6-0, 6-0 is an expected score between players of the same rating. Huh?
could you elaborate on what you mean? the expected score takes into consideration dynamic rating, not your NTPR one.
There's no system in the world that would prevent sandbagging. None. Except having all players play in one single category. Do you really want that?

Originally Posted by LuckyR View Post
Yes, if we used my proposal to use W/L to determine ranking, you are correct that somewhere between zero and 2 percent of the time it will get it wrong (in the scenario you used). But my experience is: I see way more than 2% of players in the current system at the wrong level.
really. you are sure of that. how exactly? do you have some stats? data? dizzlmcwizzl gave you a perfect example of why going by W/L is no better.

If you go by W/L, and a player wants to get bumped - he just needs to play at #3 (assuming this is a 3 players team, singles only). He is likely to play weaker opponents. You are essentially saying that a player beating 3.60 DR players 10 times is vastly better (and should get moved up) than a player who plays 3.80 DR players and has 4/6 W/L ratio. really? that is logical?

(i do think that not separating doubles and singles as far as rating is concerned is the biggest flaw of the system).
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