So I am running an experiment with three treatments. I want to see how the impact of an independent variable on the dependent variable and I want to run this for each treatment. What code could I use to do this?
To give you an example: I assigned people to watch three different news broadcast (three treatments) and then I wanted to see how their political affiliation would impact their feelings toward a policy issue. How would I run such a regression. I know the above example doesn't really make sense but basically three treatments, one specific independent variable and one specific dependent variable.