Mediation vs. Moderation
It’s easy to confuse the two. They sound similar, and while they both look at how a third variable fits into a relationship of interest, they are not the same. Let’s break it all down. In this post, we will highlight some key characteristics of mediation and moderation. We will also talk about some of the key differences between these analyses.
A mediation analysis is an extension of multiple regression. We start to think about mediation when we want to explain why or how X affects Y. This tells us more information about how or why an independent variable affects a dependent variable. The relationship between X and Y is the total effect.
In mediation, we add an independent variable called the mediator. Mediators mediate the relationship between X and Y. This occurs by X affecting M leading to M affecting Y, which is called the indirect effect. The direct effect is the relationship between X and Y in the presence of a mediator. Mediation occurs when (1) there is a statistically significant indirect effect (2) the direct effect is smaller than the total effect.
Moderation analyses look at interactions. In other words, we’re interested in whether the effect of X on Y varies depending on another variable (i.e., the moderator).
Moderator variables modify the relationship between X and Y. They affect the strength and direction of the relationship between X and Y. That means that X‘s effect on Y can change depending on the moderator.
An interaction or product term represents the moderator effect. We can calculate the interaction term by multiplying the independent variable by the moderator (X*W).
Mediators are possible explanations for a relationship between X and Y. Moderators affect the magnitude of the effect of X on Y. Another difference is in the relationship that mediators and moderators have with the independent variable. In theory, mediators result from the independent variable (i.e., X → M). On the other hand, there is no directional relationship assumed between X and a moderator (i.e., X ↔ M).
Overall, we use mediation analyses to explain relationships. We use moderation analyses to understand what variables affect the strength and direction of a relationship.
- Baron, R., & Kenny, D. (1986). The moderator-mediator variable distinction in social psychological research: Conceptual, strategic, and statistical considerations. Journal of Personality and Social Psychology, 51, 1173-1182.
- Giannoulis C. (2020). To moderate or to mediate? Retrieved from https://www.theanalysisfactor.com/to-moderate-or-to-mediate/
- James Gaskin (2018, February 05). Mediator or moderator? [Video file]. Retrieved from https://www.youtube.com/watch?v=WZr1jlKi_s0
- Statistics Soluitions (2020). What is the difference between moderation and mediation? Retrieved from https://www.statisticssolutions.com/what-is-the-difference-between-moderation-and-mediation/
- University of Wisconsin-Madison (1999). Mediator versus moderator variables. Retreived from https://psych.wisc.edu/henriques/mediator.html