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Probabilities.FPDF Method (double, int, int)

F probability density function (PDF).

Syntax
C#
Visual Basic
public static double FPDF(double x, int Nu1, int Nu2);
Parameters 
Description 
double x 
Distribution domain, real positive value or zero. 
int Nu1 
Defines distribution degrees of freedom. Nu1 must be a positive integer. 
int Nu2 
Defines distribution degrees of freedom. Nu2 must be a positive integer. 

the F probability density function (PDF) for integer parameters Nu1 and Nu2 (degrees of freedom) at the value x. Both Nu1 and Nu2 must be positive integer numbers, otherwise the result is NAN.

Calculates the Fisher (F) probability density function, defined by the equation: 

 

where n1=Nu1 and n2=Nu2 are degrees of freedom, and G is the gamma function. The most widely applied of all statistical techniques, the analysis of variance, depends heavily on the comparison of mutually independent "sum of squares" which are proportional to the chi-squared variables. The F distribution can defined in terms of a chi-squared distribution. 

In particular, any F random variable can be written as the ration of two independent chi-squared random variables, each divided by their respective degrees of freedom.

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