For Model 2, Y was a function of main effects due to two unobserved exposures (E1 and E2; both binary with frequency 0.3) and interaction effects between the exposures and G. βGE1 was always positive and less than 1, whereas βGE2 was varied between −1 and 1 by a grid of 0.1. βE1 was fixed at 0.3, whereas βE2 was fixed at 0.3 when βGE2 was positive and −0.3 when βGE2 was negative.