Author: Robert Hyatt
Date: 18:01:12 12/23/99
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On December 23, 1999 at 19:30:48, Amir Ban wrote: >On December 23, 1999 at 15:05:57, Robert Hyatt wrote: > >>On December 23, 1999 at 06:32:32, Graham Laight wrote: >> > >>>In the case of the SSDF computer pool, much of it has been there for a long >>>time, and is known to be broadly correct. >> >> >>No it isn't, but I also don't have enough time to turn this into a "statistics >>101 course" and explain why it doesn't work like that. If you look at how the >>Elo formula works, the _last_ game you played influences your rating _far_ more >>than the game you played 40 games ago. That is simply how the statistics work >>here. So even if the original SSDF programs were _perfectly_ calibrated to some >>human rating scale, the fact that 10 years has elapsed means that the effect of >>that calibration is _long gone_... >> > >The way SSDF calculate ratings, the order of games and when they were played has >no consequence at all. They calculate ratings using the entire SSDF game history >every time. It doesn't matter which game was played last. They would get the >same ratings in whatever order the matches were played. > >When the SSDF calibrated their list, they fixed some reference. Since all their >ratings are calculated in relative, not absolute terms, this reference, once >fixed, is relevant forever and can't possibly grow out of date. Had they fixed >that reference 10 points higher, for example, all ratings today would have been >exactly 10 points higher, and this will still be true in 10 or 100 years. > That is _absolutely_ a flawed way of computing ratings of course, and if that is true, the term "Elo" should _never_ be used in the same breath with "SSDF ratings". The Elo formula is quite well-defined... and the 'order' is most definitely imortant in the ratings... >Note that all this doesn't mean that the ratings may not have drifted in some >direction, but that's a different issue. > >Amir I think the 'drift' is simply caused by comp-vs-comp games, which seems to exaggerate rating differences...
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