details). The resulting equation would have 8 free parameters, just as Equation 19 does, and sex differences in the interaction would be embodied in coefficients. But, point estimates of the cross-over points for males and females still would not have SEs. In contrast, Equation 19 allows one to test specific hypotheses about sex differences in particular parameters, providing point and interval estimates of group differences on parameters that characterize the form of the interaction.
