I am struggling wih the following:

I'd like to analyze the impact of several categorical independent variables (one of them having 4 categories) and one interval IV (total score on a scale) on an interval dependent variable. Basically I would like to see the (respective) impact of all IV and test if they're significant.

I have tried lineair regression but then realized that this isn't possible because of the 1 categorical cariable with 4 categories. Making dummies also doesn't help because in that case I would only get the individual impact for the three categories, which I'm not interested in (and not the total impact of the variable). Or am I missing something here?

Tried multi-factor ANOVA (univariate) as well but I guess I shouldn't because one of the IV is an interval variable, right? SPSS then gives me several parameters for each possible score on the scale of that IV, instead of one for the total variable.

Does anyone have a solution to this?

Thanks ahead, much appreciated!