The purpose of this paper is to distinguish between the properties of moderator and mediator variables. Specifically, we differentiate between two often-confused functions of third variables: 1) the moderator function, which partitions a focal independent variable into subgroups that establish its domains of maximal effectiveness in regard to a given dependent variable, and 2) the mediator function, which represents the generative mechanism through which the focal independent variable is able to influence the dependent variable of interest. Although these third variables are different, it is not at all uncommon in organizational research to use the terms moderator and mediator interchangeably. The function of this article is to clarify the importance of respecting the distinction between the use of them. As an example of the differences between moderation and mediation variables, we suggest an application on top management teams (TMT) literature. More specifically, we offer four different kinds of hypothesis to be tested between two variables: TMT composition and firm performance, taking into account the moderation or mediation function of a third variable: intrateam conflict.
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