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Re: st: RE: Tobit coefficients


From   Richard Williams <Richard.A.Williams.5@ND.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: Tobit coefficients
Date   Fri, 27 Jul 2007 12:05:50 -0500

At 10:34 AM 7/27/2007, Austin Nichols wrote:
Vitor <vfgate-demog@yahoo.com.br>:
As I have pointed out before on this list, e.g.
http://www.stata.com/statalist/archive/2007-04/msg00549.html
http://www.stata.com/statalist/archive/2006-12/msg00466.html
-tobit- is inappropriate if the zeros are not censored values
(representing a negative y* that is observed as y=0).  If the zeros
are simply a point mass in the distribution of a nonnegative dep var,
then -poisson- or -glm- are better options.  In your case, the fact
Let me follow up with a related question for Austin or anyone else: A student of mine did a paper where she examined debt. She dropped all cases where the person had no debt. I told her that was a bad idea, but wasn't sure what a good idea was. I was thinking tobit or Heckman, but based on what Austin is saying here, is -poisson- or -glm- the way to go?


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Richard Williams, Notre Dame Dept of Sociology
OFFICE: (574)631-6668, (574)631-6463
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EMAIL: Richard.A.Williams.5@ND.Edu
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