st: tobit or anything else?

[Berthold Hoppe <berthold.hoppe@charite.de>]

Dear Statalist users!

I try to analyze the relation between two continuous biological  
markers (y, x) in a study population, where -y- depends on -x-. Other  
data indicate that this relation is significantly influenced by a  
genotype z (two outcomes: 0, 1). The hypothesis is that the  
regression coefficients (y, x) differ between z=0 and z=1.
As -y- in censored (due to lower detection limit of the measurements)  
-tobit- instead of -reg- seems to be adequate.

Would the following analysis be correct to test my hypothesis?

xi3: tobit y x@z, ll
test x@z==0 = x@z==1

Does anyone know, how to handle this question.

Have a nice weekend,
Berthold

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