Author: Sune Fischer
Date: 20:45:49 10/30/04
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On October 30, 2004 at 21:59:36, James T. Walker wrote: > >As long as you realize you are making a "best guess" and not giving a real >rating that's fine. It was of course a back of the envelope, I have not derived it rigorously. I think a more accurate guess can be made if you solve for the case where the binomial distribution should give 50% or more for the X straight wins. > The problem is that in real life untill you actually score >some real points you cannot get a score which is anything but a guess. It will always be a guess as long as all you have is a finite sample. >The >formula assumes you are 400 points below the average opponents and that is true >in both cases cited above. Nobody says it's perfect. It's only an attempt to >give a provisional score untill some concrete data is available. The 400 >points below your opponents average is as good a guess as any and easy to >calculate. The provisional score is actually a different story. You might be thinking of the Glicko system where a provisional score is used to accelerate the process. The 400 is more like a rule of thumb, it's not accurate and it's certainly not independent of the number of games. >Also how did you come up with a win expectancy of 1/4 point? Simply because >that's the next possible score closest to zero? Imagine that you have an infinitely large bag and that this bag contains infinitely many chips. You pull out 4 chips, all of them red. How certain can you be that all of the chips in the bag are red? -S. >Jim
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