StATS: Moderator variables (February 15, 2005).

I've always disliked the excessive use of detailed terminology, but when someone asked me about moderator variables, I had to look up the details. Basically, a moderator variable is one that interacts with the exposure or treatment variable. It effectively forces you to qualify your findings. Here's a published example with abstract (I have not read the full article):

As you can see, the relationship between locus of control and coping is quite different for younger individuals compared to older individuals.

Some web resources that offer definitions of moderator variables are:

There are additional terms used in the research literature such as mediator variable and intervening variable. I generally try to avoid using these terms, and even shy away from the commonly used term "confounding variable."

This page was written by Steve Simon while working at Children's Mercy Hospital. Although I do not hold the copyright for this material, I am reproducing it here as a service, as it is no longer available on the Children's Mercy Hospital website. Need more information? I have a page with general help resources. You can also browse for pages similar to this one at Category: Covariate adjustment.