When there is only one group of subjects, but they are measured more than
once, the data sets are dependent. The total variability for a single group of subjects
measured more than once is expected to be less than if the scores came from
different groups of people (that is, if the scores were independent), because interindividual
variability has been eliminated by using a single group. This tends to
reduce the MS, term in the denominator of F in a manner similar to the correction
made to the standard error of the difference in the t test (equation 8.09).