I find it challenging to interpret interaction effects in OLS multiple regression where the interactions are between two categorical variables and between two continuous variables.
Say for instance that the interaction between sexfemale: medmobility is -10.1, where sexfemale is a categorical variable with male as the reference group and medmobility is a categorical variable where low mobility is the reference group. What is the meaning of that coefficient, -10.1?
Likewise, what if you have an interaction between two continuous variables, say for instance between weight and IQ (weight:IQ) If the coefficient is, for example, 1.3 what does that mean? How does the interpretation change if both have been centered?
What about the main effects of these variables?