I am currently conducting a set of analyses examining the relationship between two predictors and an outcome. For example, the relationship between motivation (predictor 1), revision (predictor 2), and performance in an exam (outcome).
I have reason to believe that predictor 2 (e.g. revision) may mediate the relationship between predictor 1 (motivation) and the outcome (performance on the exam). I have therefore ran a mediation model and find evidence of full mediation after controlling for covariates.
I am also interested in whether a model containing the predictor (e.g. motivation) and the mediator (e.g. revision) is more predictor of the outcome than the mediator alone. Can I obtain this from the mediation model, or would I need to conduct additional analyses to examine this (e.g. separate regression analyses including only the mediator (model 1) and then the mediator and the predictor (model 2), and then compare these models)?