I am a beginner. In my research, I have four independent variables and one dependet variable. I have four hypotheses. Each hypothesis expects that the independet variable is positively associated with the depent variable. My independent variable is measured with five small items by using five-point likert scale. Therefore, each samll item has a value. I took the mean value of all five small items as the value of one corresponding independent variable in SPSS ( compute variable).Now, I want to use regression adn correlaton anlysis to test my hypothese and I want to add my company size as my control variable. However, I do not know how I can conduct this test? The value of company size is obviously not a scale variable like my dependent and indenpendet..... Does someone know how to add the control variable into my correlationa and regression analysis? The detail procedure in SPSS? Do I need to make "comoany size " as dummy variable first? But I have four categories for my company size. Thanks.