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st: RE: random effects with truncreg possible


From   "Lachenbruch, Peter" <Peter.Lachenbruch@oregonstate.edu>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: random effects with truncreg possible
Date   Mon, 11 Feb 2008 09:18:25 -0800

This sounds very much like a two-part model:  your 0 values are clearly
identified, so a logistic regression (or probit) can be used to predict
0 or non-zero, and a multiple regression model can be used for the
non-zero responses.  See an issue of Statistical Methods in Medical
Research from 2001 that has several articles on this.  They are also
called Hurdle models in Econometrics.

Tony

Peter A. Lachenbruch
Department of Public Health
Oregon State University
Corvallis, OR 97330
Phone: 541-737-3832
FAX: 541-737-4001


-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Anita
Sent: Friday, February 08, 2008 5:06 AM
To: statalist@hsphsun2.harvard.edu
Subject: st: random effects with truncreg possible

Dear Statalist Members

Sorry for posting again, I learned that I didn't explain my problem 
accurately. Sorry for any inconvenience caused.
I am currently estimating a model based on Cragg ("Some statistical 
models for Limited Dependent Variable with Application to the Demand of 
Consumer Goods", 1971)

My research topic is to compare the models used in the literature to 
explain the allocation of bilateral ODA (official development 
assistance, so money for development).
So there exist countries who do not recieve ODA (value =0) and others 
do. I do have data on both. So it is not a typical truncation problem.
First there is a selection equation to decide if a country gets ODA, I 
estimate this via a Probit Model. (y1=1 if they get ODA)
on a second step I estimate for all positive outcomes of the Probit 
Model a Regression to estimate how much money they get.

As I am working with a panel (different developing countries over time) 
I would like to do this with random effects. For Probit there exists a 
xtprobit command, for truncreg (command for the regressionpart) I didn't

find anything.
Is there a possibility to do this?
As I indicated above, I have to compare the models used in the 
literature, so I have to do Cragg's Model preferably with random effects

so I can compare with other models.

As a second question: is there a better way to solve the problem as with

truncreg? As I know, the studies used this, but it does not seem to fit 
very well

thanks a lot
Anita





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