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


From   Jacob Felson <felsonj@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: sem - is it possible to drop error terms?
Date   Tue, 12 Mar 2013 15:17:38 -0400

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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>>
>>
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> *
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--
Jacob Felson
*
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