st: differences between experimental variables with clogit

["Claudia Freese" <C.Freese@fh-osnabrueck.de>]

Dear Statalist, 

I am running a Discrete Choice experiment with 4 different brands. One 
experimental variable I am interested in is the presence or absence of an 
additional label. Stata gives me for every brand with the additional label a 
significant value, but z-values for the brands are very close to another. 

Is there a test I can use to find out if the interaction effects of brand 
and label are different from one another? Could I - for example - use the 
LR-test estimating one model with the generic variable label against a 
second one with the brand-specific label? 

Thanks,
Claudia
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