6.8. The data in Table 6.4 (from Scheffe, 1959, and in data frame genotype)

refer to rat litters the at were separated from their natural mothers at birth and given to foster mothers to rear. The rats were classified into one of four genotypes, A, B, land J. The response is the litter average weight gain, in grams, over the time of the study. The aim is to test whether the litters' and mothers' genotypes act additively and if this may be retained to test for differences in litter and mother genotype effects.