Side effect of the countback system
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Re: Side effect of the countback system
30 is based on statistical theory. A certain number of game results (n) will give you a x% probablility that your grade lies in the interval G-y to G+y. Elo has a table of y versus n (I think). I can't remember the details or the value of x Elo used or y when n=30. (I once tried working it out using my own very basic ststistics and couldn't get the same answer as Elo.)
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Re: Side effect of the countback system
There's an independent derivation in this threadMike Gunn wrote:30 is based on statistical theory. A certain number of game results (n) will give you a x% probablility that your grade lies in the interval G-y to G+y. Elo has a table of y versus n (I think). I can't remember the details or the value of x Elo used or y when n=30. (I once tried working it out using my own very basic ststistics and couldn't get the same answer as Elo.)
http://www.ecforum.org.uk/viewtopic.php?f=4&t=361
The number 8 which appears there may be of relevance since the original design of the Clarke system published your grade as being between x and x+7.