# Manuals/calci/FDIST

FDIST(x,df1,df2)

• is the value of the function
• and is degrees of freedom.

## Description

• This function gives the value of F probability distribution.
• This distribution is continuous probability distribution and it is called Fisher-Snedecor distribution.
• The F distribution is an asymmetric distribution that has a minimum value of 0, but no maximum value.
• In is the value of the function , is the numerator degrees of freedom and is the denominator degrees of freedom.
• This distribution is the ratio of two chi-square distributions with degrees of freedom r1 and r2, respectively, where each chi-square has first been divided by its degrees of freedom.
• The Probability density function of the F distribution is:

$\displaystyle f(x,r1,r2)=Γ[(r1+r2)/2](r1/r2)^r1/2*(x)r1/2-1/ Γ(r1/2)Γ(r2/2)(1+r1x/r2)^(r1+r2)/2, 0 where Γ is the gamma function.

• The gamma function is defined by Gamma(t) = integral 0 to infinity x^{t-1} e^{-x} dx.

When the value of df1 and df2 are not integers ,then it is converted in to integers.

• This function will give the result as error when
 1. any one of the argument is nonnumeric.
2.x is negative
3. df1 or df2<1 ,and  df1 ordf2>=10^10


## Examples

1. FDIST(20.6587,7,3)=0.01526530981
2. FDIST(70.120045,12.2,6.35)=0.000011229898
3. FDIST(10,1.3,1.5)=0.134947329626
4. FDIST(-28,4,6)=NAN