Author: Amir Ban
Date: 16:30:48 12/23/99
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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are calculated in relative, not absolute terms, this reference, once fixed, is relevant forever and can't possibly grow out of date.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. Note that all this doesn't mean that the ratings may not have drifted in some direction, but that's a different issue. Amir
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