13.2 Consider the SPD (CRD, RCBD) and suppose that the A-factor itself has a fac- torial structure, that is, the a levels of A are the a a2 combinations of the ai levels of factor A and the a2 levels of factor A2. Similarly, the b levels of the B-factor are the b b combinations of the b levels of factor B and the b levels of factor B2. (i) Write out a model for observations from this experiment. (ii) Write out the corresponding ANOVA table. (iii) Explain how you would test hypotheses about all main effects and interac- tions. (iv) Give the SAS commands for performing the analysis.