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.