The F distribution is also known as Snedecor's F distribution or the Fisher–Snedecor distribution.
An f statistic is given by the following formula:
Here, s1 is the standard deviation of a sample 1 with an n1 size, s2 is the standard deviation of a sample 2, where the size n2σ1 is the population standard deviation of a sample 1σ2 is the population standard deviation of a sample 12.
The distribution of all the possible values of f statistics is called F distribution. The d1 and d2 represent the degrees of freedom in the following chart: