3.5.3.1.12 Fcdf

Description

Computes \(F\) cumulative distribution function at f, with parameters ndf, fdf, and tail. The parameters of ndf and fdf must all be positive, and the values in f must be positive. The parameter tail determines the returned probability is the lower tailed or upper tailed.

The result, prob, is the probability that a single observation from a \(F\) distribution with parameters ndf and fdf will fall in the interval [0, f] for lower-tailed, [f, \(+\infty\)] for upper-tailed.

Syntax

double prob = fcdf(double f, double ndf, double fdf[, int tail])

Parameters

f

Input, the value of the\( F\) variate,\( f\). \(0\leq f<+\infty\)

ndf

Input, the degrees of freedom of the numerator variance,\(\nu_1\), must be positive (\(ndf>0.0\) ).

fdf

Input, the degrees of freedom of the denominator variance,\(\nu_2\), must be positive (\(fdf>0.0\)).

tail

Input, Optional. The tail probability type using for the F distribution

• 1 = the for upper tail probability
• 2 = the lower tail probability (Default if not set)

prob

Output, the returned probability

Example

fcdf(1000,20,20,1)=; //ANS: 9.0714457299284E-26