Programming the statistical procedures from SAS

Proc Lifereg with Weibull: Interaction with No Reference Category?

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Proc Lifereg with Weibull: Interaction with No Reference Category?

Hi,

 

I'm having an issue with a binary variable (location) coded 1/0 in a parametric Weibull survival model.  For the main effect, only one level "hip" has a coefficient value since the other is a reference, but in the interaction term the same level "knee" is not being used as a reference.  Thus in the interaction term both levels of the location variable are producing a coefficient.  I highlighted the corresponding output in yellow.  In other variables, such as race_num in this model, the main effect and interaction are working correctly.  Can someone provide some insight about what is happening here?

 

Thanks for your help.

-Carina

 

 

proc lifereg data = final ;
	class location gender revision bmi_cat race_num teaching;
	model new_time*event(0) = location race_num location*new_time race_num*new_time / dist=weibull;
	title "Model 7: Weibull Survival Model";
	format location locationF. race_num raceF.;
run;

 

 

sasout.JPG

 
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