F- Distribution

Another continuous probability distribution that finds use in econometrics is the F distribution.
If z₁ and z₂ are two chi-square variables that are independently distributed with k₁ and k₂ degrees of freedom respectively, the variable

follows F distribution with k₁ and k₂ degrees of freedom respectively. The variable is denoted by F_k1k2, where the subscripts k₁ and k₂, are the degrees of freedom associated with the chi-square variables.
We may note here that k₁ is called the numerator degrees of freedom and in the same way, k₂ is called the denominator degrees of freedom.