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01-23-2013, 09:27 AM   #32
schmke
Professional

Join Date: Jan 2010
Posts: 1,251

Quote:
 Originally Posted by LuckyR I agree with your statement. I wasn't trying to say the USTA should adopt the ATP/WTA systems, just pointing out that as a general concept, you can very successfully, treat all matches the same regardless of the ranking of the opponent.
If everyone is playing at the same level, sure. That isn't the case for USTA League play so the argument, while valid, doesn't apply. With USTA League play you have to have some measure to identify when a player should be bumped up or down. I and others have pointed out that simple win/loss is not going to be accurate and you agreed in an earlier post. And I've also said if I was to do a ratings system from scratch I would look to give some weight to win/loss so I'm not arguing it should be ignored.

Quote:
 Originally Posted by LuckyR And to be honest, I'm not even advocating totally ignoring opponent ranking, just point out that there is likely no statistical justification taking that ranking to 3 significant digits.
So, you'd advocate doing the calculations as they are now, but then rounding the dynamic rating to tenths? If so, you have several problems.

First, while your earlier statement that a 3.68 and 3.69 are not really any different and I assume you'd round both to 3.7 (?) so they are equal, you then have the problem that a 3.64 and 3.65 are near equals but when you round, they are now a tenth apart (3.6 and 3.7) which has suddenly introduced significance you didn't intend and probably isn't appropriate.

Second, a player can more easily get stuck at a rating. If they are a 3.7 and have a good match and their rating goes up to 3.74, you round them back down to 3.7. This happens again and they are again at 3.7. If you let the rating stay 3.74, that next match may improve them a bit and their steady improvement can be rewarded by gradually getting closer to 4.0 rather than having the rounding issue hold them back.

Basically, I don't see a downside to using hundredths. We all know that any given match has variables and a player may play above or below their current rating. So using hundredths and having a 3.69 and 3.68 doesn't mean the 3.69 is better or is going to win more head to head matches, it just means that is what their rating is. Dropping significant digits only causes problems like I describe above.

Now, I will grant you that if the USTA were to publish ratings more granular than half points, I would recommend only going to tenths as going farther doesn't serve much purpose. But from a calculation standpoint, at least hundredths is really required.