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Re: st: sem - is it possible to drop error terms?


From   John Antonakis <John.Antonakis@unil.ch>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: sem - is it possible to drop error terms?
Date   Tue, 12 Mar 2013 21:05:41 +0100

If you show your syntax maybe someone could help you.
Best,
J.

__________________________________________

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

Faculty of Business and Economics
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
The Leadership Quarterly
__________________________________________

On 12.03.2013 20:17, Jacob Felson wrote:
Stas,

Thanks!  Its strange -- when I try to run a basic behavior genetic
model (ACE) using Stata's sem command, I immediately receive an error
saying there are too many latent variables and the model is not
identified.  But this model is definitely identified -- at least
theoretically.  Model is here:
http://www.biomedcentral.com/1471-2202/5/49/figure/F1?highres=y

Sorry to bother you.  Any help you could provide is much appreciated.

Sincerely,

Jacob Felson



On Tue, Mar 12, 2013 at 2:59 PM, Stas Kolenikov <skolenik@gmail.com> wrote:
Jacob,

you can constrain the variance of these error terms to zero with
-variance()- option of -sem-.

-- Stas Kolenikov, PhD, PStat (SSC)
-- Senior Survey Statistician, Abt SRBI
-- Opinions stated in this email are mine only, and do not reflect the
position of my employer
-- http://stas.kolenikov.name



On Tue, Mar 12, 2013 at 1:53 PM, John Antonakis <John.Antonakis@unil.ch> wrote:
Hi Jacob:

You need to be much more specific about what specific model you wish to test
(write-out equations or syntax). Most probably don't know what ACE is:

http://www.stata.com/support/faqs/resources/statalist-faq/

Best,
J.

__________________________________________

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

Faculty of Business and Economics
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
The Leadership Quarterly
__________________________________________


On 12.03.2013 19:30, Jacob Felson wrote:
I'm wondering if its possible to drop the error terms that are
included by default in sem models.  I've searched in the manual and
online but I can't find any indication that this is possible.  I
imagine its not, but I wanted to check with the experts to make sure.

(I'm estimating a behavior genetic model with data on MZ and DZ twins
-- the so-called ACE model.)


Thank you,


Jacob Felson
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--
Jacob Felson
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