--- georg wernicke <[email protected]> wrote:
> The complete references are:
>
> Marno Verbeek,
> A guide to modern econometrics.
> 2000
> John Wiley & Sons,
>
> and
>
> Linders, G. J. M. and H. L. F. de Groot (2006). Estimation of the
> Gravity Equation in the Presence of Zero Flows.
Thanks
> when using stata for the heckman it will ask you for a selection
> dependent variable. use the dummy for that.
-heckman- asks you for the selection equation. This may or may not
contain the dummy you refer to. If you whish to include that dummy, you
must use the second syntax shown in -help heckman- (otherwise -heckman-
will fail). This dummy does not need to be specified, but there may be
situation where it might be practical. However, it has nothing to do
with Seema's question, as I explained in my previous posts.
Hope this helps,
Maarten
-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands
visiting address:
Buitenveldertselaan 3 (Metropolitan), room Z434
+31 20 5986715
http://home.fsw.vu.nl/m.buis/
-----------------------------------------
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