# Difference between revisions of "Manuals/calci/FDIST"

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*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. | *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: | *The Probability density function of the F distribution is: | ||

− | <math>f(x, | + | <math>f(x,r_1,r_2)=\frac{\Gamma[\frac{r_1+r_2}{2}](\frac{r_1}{r_2})^{\tfrac{r_1}{2}}}{ \Gamma(\frac{r_1}{2})\Gamma(\frac{r_2}{2})}*\frac{(x)^{\tfrac{r_1}{2}-1}}{(\frac{1+r_1x}{r_2})^{\tfrac{r_1+r_2}{2}}}</math> |

+ | 0<x<\infty</math> where Γ is the gamma function. | ||

*The gamma function is defined by Gamma(t) = integral 0 to infinity x^{t-1} e^{-x} dx. | *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. | When the value of df1 and df2 are not integers ,then it is converted in to integers. | ||

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2.x is negative | 2.x is negative | ||

3. df1 or df2<1 ,and df1 ordf2>=10^10 | 3. df1 or df2<1 ,and df1 ordf2>=10^10 | ||

− | |||

==Examples== | ==Examples== |

## Revision as of 01:12, 8 January 2014

**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:

0<x<\infty</math> 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

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

## See Also