The full linear regression model, allowing for additive, dominance and epistatic effects of the two loci on the average phenotype and linear response to the covariate (G × E) was fitted to the data generated under each of the five models for genetic and environmental effects (above). The raw trait values, sum scores for the two simulated tests and transformed scores for the first test were all analyzed on the assumption of normal errors. The dichotomous disease phenotypes were analyzed by logistic regression assuming binomial errors. In addition to the full model, the “true” model, assumed in generating each data set, was fitted and a variety of reduced models that were expected to illuminate errors of inference that might attend the unwary.
