Direct Versus Indirect Mediation Effects
In the diagram shown above, the indirect effect is the product of path coefficients "A" and "B". The direct effect is the coefficient "C". The total effect measures the extent to which the dependent variable changes when the independent variable increases by one unit. In contrast, the indirect effect measures the extent to which the dependent variable changes when the independent variable is held fixed and the mediator variable changes to the level it would have attained had the independent variable increased by one unit. In linear systems, the total effect is equal to the sum of the direct and indirect effects (C + AB in the model above). In nonlinear models, the total effect is not generally equal to the sum of the direct and indirect effects, but to a modified combination of the two.
Read more about this topic: Mediation (statistics)
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