thanks for your response
I notice that this is a stepwise sort of procedure.
Since I'm only interested in main effects and interaction effects when everything else is controlled for, I can enter all four IVs and their possible interactions all at once right?
Or should I enter one interaction effect at a time?
Sorry, that was probably a very unclear question...
edit:
I guess I just don't understand all the stepwise stuff. Why can't you just put in all the variables and interactions you're interested in at once? Could someone explain that part more succintly to me?