Hello
I am looking at the interaction between age (dichotomized as above OR below 65 years) and sex (men versus women) on the functional outcomes of therapy. In my model, I would like to insert 3 independent variables: age sex agexsex
While creating the interaction variable, I just created a column of data representing agexsex. Following this, I conducted regression analysis using SAS code:
Proc reg data = Knee_gender_interaction2; model IADL_6months = age sex agexsex/stb clb; model functions_6months = age sex agexsex/stb clb;
run;
The problem I run into is that SAS is not allowing me to get the beta estimate for the interaction term agexsex, by suggesting that the age-sex is the linear product of age and sex which are also present in the model.
I read somewhere that I should create a summy variables to test the effect of all 3 independent variables: age, sex, and agexsex.
Can somebody suggest teh SAS coding for creating the dummay variable and subsequent regression model?
Thank you much.
Saurabh
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