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# Re: st: how to test equality of coefficients - ivreg e suest?

 From John Antonakis To statalist@hsphsun2.harvard.edu Subject Re: st: how to test equality of coefficients - ivreg e suest? Date Thu, 14 Feb 2013 18:02:23 +0100

Ah....OK. Then set it up as a multiple group SEM (i.e., you have two groups/samples of observations and you want to check for cross group parameter constraints). This is like a -suest-, but you can do multiple equations.
```
See -help sem-

Best,
J.

__________________________________________

John Antonakis
Professor of Organizational Behavior
Director, Ph.D. Program in Management

University of Lausanne
Internef #618
CH-1015 Lausanne-Dorigny
Switzerland
Tel ++41 (0)21 692-3438
Fax ++41 (0)21 692-3305
http://www.hec.unil.ch/people/jantonakis

Associate Editor
__________________________________________

On 14.02.2013 17:16, Manuela Deidda wrote:
```
```Dear John,
However, I have some doubts regarding this solution.
Indeed, the gmm solution in the thread works when, given the
dependent variable Y and the indicator variable I (determining whether
Y belongs to group 1 or to group 2):

Y=Y1 if I=1 and 0 otherwise
Y=Y2 if I=0 and 0 otherwise

My situation is more like this:
Y=Y1 if I=1 and missing otherwise
Y=Y2 if I=0 and missing otherwise

In the first case, one estimates coefficients through the whole sample
(simply, you have that the variable is truncated at zero).
In the second case, you want only to estimate coefficients in the
subsample where you estimate the variable.

Ex. if n=1000
I=1 if _n=1/250
I=0 if _n=251/1000

I simply need to estimate Y1 when I have 250 observations and Y2 when
I have the other 750 obs...

How can I deal with this?

Best,
M.

2013/2/14 John Antonakis <John.Antonakis@unil.ch>:
```
```Try

http://www.stata.com/statalist/archive/2011-11/msg00487.html

This is a very elegant and quick solution:

Best,
J.

__________________________________________

John Antonakis
Professor of Organizational Behavior
Director, Ph.D. Program in Management

University of Lausanne
Internef #618
CH-1015 Lausanne-Dorigny
Switzerland
Tel ++41 (0)21 692-3438
Fax ++41 (0)21 692-3305
http://www.hec.unil.ch/people/jantonakis

Associate Editor
__________________________________________

On 14.02.2013 13:02, Manuela Deidda wrote:
```
```is there any way to compare equality of estimated coefficients after
ivreg?
I have to estimate an iv regression in two different subsamples, defined
by
the dummy variable I:
1) I=1
2) I=0

with regress one can use suest to compare coefficients in a sample
split.
Is there a way to do something similar after ivreg?

Any help is appreciated,
thanks a lot!
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