Hi everyone, I am helping out a friend with the data analysis portion of her master thesis. I have been doing research on the topic of moderation and mediation (and learned quite a bit), but so far I have not being able to figure out how to perform moderation analysis for her study. In my friend's study, she is testing whether perception (the moderator) moderates the relationship between eating disorder (the Dependent Variable) and family cohesion (the Independent Variable). All three variables are measured on a continuous scale, which is the ideal situation. However, her thesis adviser insists that family cohesion be categorized into 3 groups: low, medium, and high. I told my friend this results in a significant loss in information, but she said the categorization would allow her to test for differences between the 3 groups. In summary, her model involves a continuous DV, a categorical IV, and a continuous moderator. I understand in the case where all variables are continuous, the analysis would entail a multiple regression that regresses the DV on the IV, the moderator, and the product term between the IV and the moderator. And significance of the product term is an indication of a moderating effect. But in the model specified by my friend, how do we go about testing for moderating effects? (I realize that the categorical IV must be represented by 2 dummy variables in the regression model. Do I multiply each of them by the moderator?) Any suggestions would be much appreciated!