F Test

F-tests get their name from the F test statistic, which was named after Sir Ronald Fisher. The F-statistic is just a two-variance ratio. Variances are a metric for dispersion, or how far the data deviates from the mean. Greater dispersion is shown by higher values.

The square of the standard deviation is the variance. Because standard deviations are in the same units as the data rather than squared units, standard deviations are easier for us to understand than variances. Many analyses, however,...