Author: Dieter Buerssner
Date: 13:07:33 04/19/05
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On April 19, 2005 at 03:27:48, Odd Gunnar Malin wrote: > // Alghorithm from Simon Schmitt's site on the net. > > // Die offiziellen Elo-Zahlen werden nach folgender Formel errechnet: > // Erwartung = 0,5 + 1,4217 x 10^-3 x D > // - 2,4336 x 10^-7 x D x |D| > // - 2,5140 x 10^-9 x D x |D|^2 > // + 1,9910 x 10^-12 x D x |D|^3 > > // wobei gilt: > // D = Differenz = Elo(eigene, alt) - Elo(Gegner, alt) > // |D| = Absolutbetrag von D Interesting. I tried to reproduce the tables given by FIDE and the German chess federation, and got very close results to the numbers given. However in the tails, the error was larger than just a rounding error. I had tried formulas based on the logistic distribution (they were given earlier in this thread, too), and based on normal distribution. Both ´formulas give very similar numbers, unless in the extreme tails of the distribution. The numbers listed in the tables were somewhere in between ... Above formula looks like the author had a pocket calculator without scientific functions, and neither had a logarithmic table book, nor a (good) slide rule :-) Well, above formula can be calculated with a pen only in reasonable time. It may also be the case, that he really wanted the normal distribution. The formula for the score uses the error function erf() then, which really will not be on a slide rule. I think it could not easily be inverted for calculation of D. Regards, Dieter
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