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Old 12-03-2012, 11:55 PM   #34
gameboy
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Folks, this is pretty standard math we are talking about here. I understand many of you don't use that much math in your everyday life, but ignorance is not something to be proud of.

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Originally Posted by LuckyR View Post
1- I don't personally believe that how well any player plays the game of tennis can be quantified to three significant digits. Sure the ratings exist, but IMO the science of using rating numbers to predict outcome of matchplay is too poor to justify that level of implied confidence. In my experience the standard deviation of quality of play is so wide that 2 significant digits is suspect, if you don't believe me, ask Lukas Rosol...
Good, you don't have to believe anything. These are all based on facts, stats and numbers. There is nothing to believe.

You say that "science" is too poor. Can you give me some scientific background for that? This is pretty much the same formulas used for every other sports (including Vegas odds) and what Nate Silver used to predict 50 out of 50 state election results. Everybody who knows anything about statistics use it, so why is the "science" poor? I am sorry but "because I said so" is not an acceptable answer.

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Originally Posted by LuckyR View Post
2- Regardless of the numerical system, there are players whose numerical rating does not correlate to their quality of play, on purpose, that is they give false information to manipulate the rating. That difference I call Sandbagging and can result in playing matches against better competition who have lower ratings. I was trying, unsuccessfully, to explain that nuance in my last post, first paragraph.
Sandbagging happens with any stratified system. It is not unique to this system.

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Originally Posted by LuckyR View Post
3- I agree that no system will "prevent" sandbagging. As long as people are willing to throw matches completely that will be possible. But this system creates sandbaggers. Using your scenario, the player who is 3.99, will likely always play someone lower rated than they are and thus will go 15-0, as you cite. The system is completely unequipped to deal with the 3.99 who improves their quality of play, yet never "plays up" to 4.5 (as a 4.0). Never gets to demonstrate their improvement against better competition and never gets moved up.
You lost me here.

It is clear that you do not understand how this system works. A 3.99 player can ALWAYS move up based on the current system. All you have to do is do better than expected. If a 3.99 plays 3.75 (average player), the 3.99 is expected to win a competitive match (say, 6-3, 6-4). However, if the match is not competitive (say 6-1, 6-1), the 3.99 player will get bumped up.

You really should understand how the system works before criticizing it.

Quote:
Originally Posted by LuckyR View Post
4- You are right that a straight W/L system will incorrectly bump people up who just randomly happened to play a bunch of players at the low end of the scale, you noted that a 3.89 (in the absence of sandbagging) would do so about 2% of the time in a 15 match season. OK you got me, you keep that guy at 4.0, I move him up (incorrectly BTW 2% of the time, your number) to 4.5 Well that 2% of the time in my system what happens? He gets killed playing 4.25s as a 3.89. Next season, he's a 4.0 Self correcting system. At least as a consolation, in a W/L system, no one wonders "why am I playing the 15-0 guy from last year?"
The current system is also self correcting - if you get bumped up and you are not competitive, you will get bumped down. But this system is better since people at the very top/bottom of the level won't get yo-yo'ed up and down every year. Again, learn the system and you won't wonder "why am I playing the 15-0 guy from last year."

Quote:
Originally Posted by LuckyR View Post
5- The unaddressed issue is the opposite scenario: what about the 4.11 (playing 4.5) who goes 0-15 for the exact same reason the 3.89 goes 15-0? Does that guy get a break? Nope.
It is addressed. If you do worse than expected, you will get bumped down. If you are competitive in most of your matches, there is no need to bump down, just because you are unlucky and lose all of your matches.

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Originally Posted by LuckyR View Post
6- How better to acknowledge that you do in fact know what a simple mathematical computation is more clearly than by stating: "As you know..."?
????

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Originally Posted by LuckyR View Post
7- When you beat someone or get beat 6-0, 6-0 do you think: "I think we were probably mismatched" or "logical score between correctly rated players"? Of course both are possible (what the USTA says), but in your opinion which is more likely?
It would be the exact same chance as someone playing an opponent full level or more above/below. Not sure what your point is.

Quote:
Originally Posted by LuckyR View Post
Ultimately it boils down to this: what is more likely to happen and what is more likely to kill the fun factor of league play: A) a system that thinks it can predict outcomes by rating and only moves players relatively if they behave unexpectedly and beat a "better" player, regardless of how many "lesser" players they smear the court with or B) a system that acknowledges that matchplay is unpredictable for numerous reasons (I agree cheating is one, but a rare one) and figures that the quality of opponents will even out in the end, so a 15-0 guy is likely better than his competition and moves him up?

Either is reasonable but I feel, obviously, that B is less likely to mislabel players, especially in the long haul, as it is self correcting
Both systems have been tried. The current one was adopted because there were more problems with the old one.

Last edited by gameboy : 12-03-2012 at 11:59 PM.
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