st: reduced form reg

[Viktor Slavtchev <viktor.slavtchev@uni-jena.de>]

Dear,
I have followed question.
I know that y1 depends on x1 in the way:
y1 = x1 + Z1 + e1.
However, I also  am interested in the impact of both y1 as well as x1 on 
y2. y2 is given by:
y2 = y1 + x1 + Z2 + e2.

So, I have in mind a reduced form model for y2:
y2 = e1 + x1 + Z2 + e2.
But:
y1={0;1;2;3} Likert-scale variable, hence I am going for ologit in order 
to estimate y1 = x1 + Z1 + e1.
y2 is an overdispersed count variable; therefore I have to use negbin.

Are there any problems if I estimate the reduced form y2 = e1 + x1 + Z2 
+ e2, knowing that in the first step ologit has been used and in the 
second step I have to use negbin?

Thanks
Viktor

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