Adjusting for a Mediator in Models With Two Crossed Treatment Variables
Open Access
- 4 March 2008
- journal article
- research article
- Published by SAGE Publications in Organizational Research Methods
- Vol. 11 (2), 224-240
- https://doi.org/10.1177/1094428106296639
Abstract
In a simple mediation model, the effect of a manipulated variable X on a dependent variable Y over and above the effect of the mediator Me can be estimated by regressing Y on X and Me. The impact of X on Y in such a model is adjusted for the relationship both between X and Me and between Me and Y. The authors examine the adjustment function in the context of a 2 × 2 design with two manipulated variables. In such a situation, the mediator could be affected by either one of the main effects and/or the interaction between two manipulated variables. To adjust for the impact of the mediator, a standard procedure has been to rely on an ANCOVA that includes only the mediator. The authors show, both analytically and with simulations, that this leads to improper control of the mediator and to biased estimates of the model parameters.Keywords
This publication has 6 references indexed in Scilit:
- Is “service with a smile” enough? Authenticity of positive displays during service encountersOrganizational Behavior and Human Decision Processes, 2005
- When moderation is mediated and mediation is moderated.Journal of Personality and Social Psychology, 2005
- Adjusting researchers’ approach to adjustment: On the use of covariates when testing interactionsJournal of Experimental Social Psychology, 2004
- A comparison of methods to test mediation and other intervening variable effects.Psychological Methods, 2002
- A Simulation Study of Mediated Effect MeasuresMultivariate Behavioral Research, 1995
- The moderator–mediator variable distinction in social psychological research: Conceptual, strategic, and statistical considerations.Journal of Personality and Social Psychology, 1986