Which of the following is not one of the conditions that must be checked in order for the calculated F-statistic to follow the F-distribution.

A) The groups are independent of each other.

B) Each group's population must be at least 10 times larger than its respective sample.

C) The distribution of the observations is Normal in each group's population or the sample size is large.

D) The variances or standard deviations of the groups must be equal.