Tamara,
Take a look at the sample selection models-particularly, the Heckman selection model.
Regards,
Bob Yaffee
Robert A. Yaffee, Ph.D.
Research Professor
Shirley M. Ehrenkranz
School of Social Work
New York University
home address:
Apt 19-W
2100 Linwood Ave.
Fort Lee, NJ
07024-3171
Phone: 201-242-3824
Fax: 201-242-3825
[email protected]
homepage: http://homepages.nyu.edu/~ray1/
----- Original Message -----
From: Tamara Pejovic <[email protected]>
Date: Wednesday, August 22, 2007 9:45 am
Subject: st: Two part model - How to combine models?
To: [email protected]
> Hi,
> I have a quick question. I have a response variables that is
> positively
> skewed and contain a substantial proportion of zeroes. Since a common
>
> method for analyzing this type of data is a two-part model I have the
>
> analysis of three stages:
> The first involved creating two sets of data from the original: one
> showing whether or not the problem is present and the other indicating
>
> the "level of the problem" when problem is present.
> The second stage involved modelling occurrence of problem, using
> logistic regression, and separately modeling the level data using
> ordinary regression.
>
> Finally, the third stage should be combining the two models in order
> to
> estimate the expected "level of the problem" for a specific set of
> values of possible predictors.
>
> My question is how to do this? Is it just enough to multiple
> probabilities using conditional probabilities rule? Does STATA have a
>
> module for solving two-part models?
>
> Thanks,
> Tash
>
>
> *
> * For searches and help try:
> * http://www.stata.com/support/faqs/res/findit.html
> * http://www.stata.com/support/statalist/faq
> * http://www.ats.ucla.edu/stat/stata/
*
* For searches and help try:
* http://www.stata.com/support/faqs/res/findit.html
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/
