Plot interaction effects

FDFS

New Member
#1
Hi!

I already know how to plot the predicted probabilities of binomial models without any interaction terms:

predicted logit = a + bX

predicted probabilities= EXP(predicted logit)/(1+EXP(predicted logit))

What I needed to know is how to do it when the model contains an interaction. For simplicity's sake the model we're talking about has only one IV (scale ranging from 0 to 10) and one moderator (ordinal ranging from 1 to 4), which means obviously the interaction is between the two of them. Which equation should I follow to plot the predicted probabilities graph of this interaction?

Thank you for your help.
 

hlsmith

Less is more. Stay pure. Stay poor.
#2
I believe typically you would plot four lines (stratified by moderator). You would then see the lines cross of have different slopes or shapes (depending on the types of responses you got for the first IV).
 

FDFS

New Member
#4
I believe typically you would plot four lines (stratified by moderator). You would then see the lines cross of have different slopes or shapes (depending on the types of responses you got for the first IV).
Yes, but that I could do that even without the interaction term, right? What would be the advantage of including the interaction term, then? And would that still capture the interaction between the two variables?
 

hlsmith

Less is more. Stay pure. Stay poor.
#5
Is your interaction term significant? If so, you would want to control for it, since your beta coefficients will be adjusted when it is in the model.