Post-hoc probing of significant moderational and mediational effects in studies of pediatric populations.

OBJECTIVE To provide examples of post-hoc probing of significant moderator and mediator effects in research on children with pediatric conditions. METHODS To demonstrate post-hoc probing of moderational effects, significant two-way interaction effects (dichotomous variable x continuous variable; continuous variable x continuous variable) were probed with regressions that included conditional moderator variables. Regression lines were plotted based on the resulting regression equations that included simple slopes and y-intercepts. To demonstrate probing of mediational effects, the significance of the indirect effect was tested (i.e., the drop in the total predictor --> outcome effect when the mediator is included in the model), using Sobel's (1988) equation for computing the standard error of the indirect effect. RESULTS All significant moderator and mediator effects are presented in figure form. CONCLUSIONS The computational examples demonstrate the importance of conducting post-hoc probes of moderational and mediational effects.