Statalist


[Date Prev][Date Next][Thread Prev][Thread Next][Date index][Thread index]

Re: st: Two part model - How to combine models?


From   "E. Paul Wileyto" <epw@mail.med.upenn.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Two part model - How to combine models?
Date   Wed, 22 Aug 2007 10:06:06 -0400

Look up Stata help on zip, zinb, ztp, ztnb. I thought there was also a zero-inflated binomial, but I can find no reference to it.

P

Tamara Pejovic wrote:

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/

--
E. Paul Wileyto, Ph.D.
Assistant Professor of Biostatistics
Tobacco Use Research Center
School of Medicine, U. of Pennsylvania
3535 Market Street, Suite 4100
Philadelphia, PA 19104-3309

215-746-7147
Fax: 215-746-7140
epw@mail.med.upenn.edu
http://mail.med.upenn.edu/~epw/
*
* 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/




© Copyright 1996–2014 StataCorp LP   |   Terms of use   |   Privacy   |   Contact us   |   What's new   |   Site index