A mediating variable, also known as a mediator variable, intermediary variable, or intervening variable, is a third hypothetical variable that explains the mechanism or process that underlies an observed relationship between an independent variable and a dependent variable). Rather than a direct causal relationship between the independent variable and the dependent variable, a mediation model proposes that the independent variable influences the mediator variable, which in turn influences the dependent variable). In other words, a mediator variable explains the relationship between two other variables.

To identify a mediating variable, researchers can follow the steps outlined by Baron and Kenny:

1. Regress the dependent variable on the independent variable to confirm that the independent variable is a significant predictor of the dependent variable.
2. Regress the mediator on the independent variable to confirm that the independent variable is a significant predictor of the mediator.
3. Regress the dependent variable on both the independent variable and the mediator variable to confirm that the mediator variable is a significant predictor of the dependent variable, even when controlling for the independent variable.

If the mediator variable is a significant predictor of the dependent variable, even when controlling for the independent variable, then it is considered a mediating variable.

Mediating variables are different from moderator variables, which affect the strength or direction of the relationship between two variables, but do not explain the relationship itself.