I am doing a simple marketing project that has the following types of variables:
- X1 - continuous (e.g. income)
- X2 - categorical (e.g. gender)
- Y - continuous (e.g. number of a product type purchased such as tubs of ice-cream)
I am interested in the relationship between income (X1) and product purchase (Y) but also the effect of gender (X2) on this relationship. (i.e. interaction or moderation effect).
I have centered X1 and have used the general linear model in SPSS. The result on Y is as follows:
- X1 - significant
- X2 - not significant
- X1*X2 - not significant
How do I interpret this result in terms of main effect and interaction?