HI Statalist,
I have a question about heckman's selection probit model (heckprob).
It sounds really weird, but it turns out that the outcome changes as the order of independent variables changes.
That is,
heckprob y1 x1 x2 x3, s(y2 x11 x12 x13)
heckprob y1 x2 x1 x3, s(y2 x11 x12 x13)
have different outcomes for x1 and x2 in both Stata 10 and 11
Even worse is that results vary across the version of Stata. Not only does each version show the same variable order issue, but even the same model shows different results across the version.
Please help me out to address this issue.
I also wonder if you have any alternatives to heckprob.
Chungshik Moon
Ph.D. Candidate
Department of Political Science
Florida State University
-Everything is possible for him who believes.
(Mark 9:23)
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