Help - controlling for variables in moderation analysis

#1
Hi everyone,

I need some help with my dissertation analysis.

I am doing a moderation analysis. I have 2 dummy coded categorical IVs, a continuous moderator, and a continuous DV.

I understand how to run the moderation (variables in step 1 of regression, product terms in step 2).

But how do I control for another variable? My groups differ on a categorical variable and I want to control for this when I run the analysis.

I'd appreciate any help - my dissertation is due on Friday!
 

trinker

ggplot2orBust
#2
Depending on the program you're using you'll want to dummy code the categorical variable and then enter it into the model in the first step before anything else. This method is called hierarchical multiple regression (do not confuse with hierarchical linear model). You'll be interest in the change in F values and the change in R values above and beyond this control variable.