Originally Posted by jmnk
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.
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. 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.
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?
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.