The F-distribution reference article from the English Wikipedia on 24-Apr-2004
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F-distribution

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In statistics, the F-distribution is the probability distribution of a random variable of the form

where

The F-distribution arises frequently as the null distribution of a test statistic, especially in likelihood-ratio tests, perhaps most notably in the analysis of variance.

If d2 > 2, then the mean is d2/(d2 − 2) and if d2 > 4 the variance is given by

The F-distribution always ranges from zero to infinity; if d1 > 2, it is a unimodal with mode

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