Abstract: The concepts and analyses of the moderator and mediator effects were discussed. Approaches in estimation and testing of moderating and mediating effects were summarized with recommendations for appropriate choices. The moderator and mediator as well as their effects were compared in terms of their implications, intentions, functions, implied models, estimation and testing strategies and other factors which enable a better understanding of the two variables involved. As an illustration, moderators and mediators were analyzed and compared in a study on the relations between students’ antisocial behaviors and peer relations.

Key words: moderator, moderating effect, mediator, mediating effect