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st: How to perform a -clogit- on a choice-based AND exogeneously stratified sample


From   Simon Coulombe <simoncoulombe@gmail.com>
To   statalist <statalist@hsphsun2.harvard.edu>
Subject   st: How to perform a -clogit- on a choice-based AND exogeneously stratified sample
Date   Tue, 24 Mar 2009 10:25:17 -0400

Dear Statalist,

         I am currently trying to perform a -clogit- on a stratified
sample.  The stratification is both choice-based and exogenous,  as
the persons running the survey wanted to have the same amount of
persons for each *options* and for each *area*.

       For example, suppose that in real life there are
10 persons in Region A using option 1
20 persons in Region A using option 2
30 persons in Region A using option 3
150 persons in Region B using option 1
250 persons in Region B using option 2
350 persons in Region B using option 3

        then my sample will look like this:
5 persons in Region A using option 1
5 persons in Region A using option 2
5 persons in Region A using option 3
5 persons in Region B using option 1
5 persons in Region B using option 2
5 persons in Region B using option 3


      How would you correct the  clogit estimates to take this into account?

   I know from  chapter 8 "Discrete Choice Analysis : Theory and
Application to  Travel Demand" written in 1985  by Ben-Akiva &  Lerman
  that only the intercept will be affected in a choice-based sample
and that I can correct it easily.    I am not sure what to do with the
exogeneous part though.

Can stata handle this?

Thanks,
Simon
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