Research Skills: Week 90

MEDIATION ANALYSIS

Learn
Simple regression is used to examine the relationship between one dependent and one independent variable. After performing an analysis, the regression statistics can be used to predict the dependent variable when the independent variable is known. Regression goes beyond correlation by adding prediction capabilities.

Unlearn
In addition to simple regression analysis, there is a different type of analysis called mediation analysis.

Relearn
What is Mediation?
A statement about causality
When the effect of one variable (X) on another variable (Y) is through the effect of a third variable (M)
Also referred to as an “indirect effect”
Mediation analysis has three equations
Y= i1 + cX + r
Y= i2 + c’X + bM + r
M= i3 +aX + r
i1, i2, and i3 are intercepts

Methods for Testing Mediation: Causal Steps Approach
Mediation occurs based on four conditions
There is a relation between X and Y
Changes in IV account for changes in the mediator
Changes in mediator account for changes in the DV when both IV and mediator are predictors
The coefficient relating the IV to the DV is reduced when the mediator is included
Complete mediation vs. partial mediation

However there are limitations with regards to causal steps approach.
Firstly, here is not a joint test of the conditions
Secondly, it does not provide a direct estimate of the size of the indirect effect, nor the significance of the indirect effect
Thirdly, it has low power.