320 REPEATED-MEASUREMENT AND OTHER EXPERIMENTAL DESIGNS (2—1)(5—1) <4. The S/R term is the variation within subjects summed over groups, and the degrees of freedom are R(n— 1) < 2(4— 1) —6. The SC/R term is the subject-by-column interactions summed over rows, and the degrees of freedom are R(n— idte-t)< U(4—- I)(5— 1) < M4. The appropriate error term for testing row effects is the S/R variance estimate. The appropriate error term for testing column effects and R x C interaction is the SC/R variance estimate. The F ratios are as follows: Sr 3240 seo 31.53 F. st 436 7.23 p<.OI AT Fezipo- ze —644 pel In this illustrative example the row effects are not significant, whereas the column effects, row-by-column effects, and row-by-column interaction are significant at better than the .01 level. 19.40 ASSUMPTIONS UNDERLYING REPEATED- MEASUREMENT DESIGNS A basic assumption in the analysis of variance is the homogeneity of variance assumption. In, for example, a simple analysis of variance in- volving k independent groups this assumption may be stated in the form oj? co? <<