F Distribution. The F distribution (for x > 0) has density function (for = 1, 2, ...; = 1, 2, ...):

f(x) = {[(+)/2]}/[(/2) *(/2)]*(/)/2 *
x(/2)-1 * {1+[(/)*x]}-(+)/2

0 x <
= 1, 2, ...,    = 1, 2, ...

where
,   are the degrees of freedom
        (gamma) is the Gamma function.


The animation above shows various tail areas (p-values) for an F distribution with both degrees of freedom equal to 10.
statická ukážka