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Old 01-24-2013, 02:09 PM   #46
LuckyR's Avatar
Join Date: Jun 2006
Location: The Great NW
Posts: 6,355

Originally Posted by NumbersGuy View Post
For those wondering what the statistical difference is between a 3.68 and a 3.69, see the table below Using a methodology very similar to Schmke's (so I don't have everyone's true NTRPs, just my estimates), and a large database of over 20,000, here's what I calculate. I sure hope the table comes out legibly.

[Rating difference] [% won by higher player]
0.00-0.01 52%
0.01-0.05 55%
0.05-0.10 63%
0.10-0.15 69%
0.15-0.20 72%
0.20-0.25 77%
0.25-0.30 80%
0.30-0.35 83%
0.35-0.40 86%
0.40-0.45 89%
0.45-0.50 91%

I suspect the percentages for the upper categories are somewhat artificially depressed by tanking, but of course have no proof.

So the answer to 3.68 vs. 3.69 is one could expect the 3.69 to win about 52% of the time, based on this admittedly limited sample and imperfect NTRP calculation method.

Wow, that looks like a lot of work (the adding of your estimation of the NTRPs, not the calculation itself).

Of course to get the actual data (perhaps similar or identical to your estimate, or not...) it would not take nearly the effort for the USTA.

A 2% difference by your estimate (using 50% as the standard), seems reasonable at first glance, of course the number is meaningless (or more meaningless, since it is your estimation of the true NTRP) without a mention of the error of the calculation.
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