I am interested in studying the interaction with a ordinal predictor p and continuous moderator m on an outcome y with a simple model of:
y ~ p + m + p*m
However, since my predictor is categorical, it is easier for me to plot how the relationship between outcome y and moderator m (both continuous) changes for different categories of predictor p.
That is, y is on the y axis, m is on the x axis and I draw several lines with different slopes for each category of predictor p. Would this be a valid way to plot the interaction effect if I am ONLY interested in the moderation effect of m and not its direct relationship with outcome y?
I think it is because if there is an interaction effect, then it should be bidirectional- that is, m modifies the relationship between y and p and p would modify the relationship between y and m, is that correct?