Table : TABLE 12-11. Calculating Sample Variances We calculate the variances of the samples by dividing each sum of squares by the sample size minus 1 to check one of the assumptions of ANOVA. For unequal sample sizes, as we have here, we want the largest variance (20.917 in this case) to be no more than twice the smallest (13.0 in this case). Two times 13.0 is 26.0, so we meet this assumption.