Types of “Third” Variables

Question 1

What are the variables?

Answer 1

• Confounding
• Moderating
• Mediating

Question 2

Confounding

Answer 2

• A variable is associated with both the exposure (independent variable) and the outcome (dependent variable), but does not lie on the causative pathway.
• Can account for all or part of an apparent association between an exposure and an outcome
• Needs to be accounted for to prevent distortion of results

Question 3

Moderating

Answer 3

• A variable that alters the strength and/or direction of the relationship between the independent variable and the dependent variable such that the relationship between the independent variable and the dependent variable depends on the values of the moderator.
• An exposure has a different effect among different subgroups

Question 4

Mediating

Answer 4

• An intermediate or intervening variable in a causal chain relating an independent and a dependent variable.
• The most basic mediation model is one where an independent variable leads to changes on a mediator, which, in turn, causes changes on a dependent variable.