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Re: st: Implementation of Latent Variable Model with SEM Builder


From   John Antonakis <John.Antonakis@unil.ch>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Implementation of Latent Variable Model with SEM Builder
Date   Sat, 14 Apr 2012 10:15:08 +0200

Hi:

You need to do (latent variables are in CAPS in Stata and I am assuming education is categorical):

xi: sem (OBJ_HEALTH->blood chronic limit) (sah<-age i.education OBJ_HEALTH)

If sah is not truly continuous but ordered, then I am afraid you cannot use Stata here (MPlus could do this for you--hope that Stata Corp adds the option to use categorical and ordered dependent variables in sem in the future). Other thing to do would be to create an index of objective health and then to simply estimated it with

oprob sah age i.education index_obj_health

HTH,
J.

__________________________________________

Prof. John Antonakis
Faculty of Business and Economics
Department of Organizational Behavior
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 14.04.2012 07:55, Samantha Molbach wrote:
Dear Statalisters,

I need some help in implementing a Structural Equation Model in Stata
12. I want to create a health index according to Bound (1999): "The
dynamic effects of health on the labor force transitions of older
workers".

I have the following variables available: Self-assessed health on a
five-point scale (SAH), Age, Education, different objective measures
of health such as blood pressure (Blood), chronic diseases (chronic)
and physical limitations (limit).

The theoretical model is the following:
H = X*ß1 + Z*ß2 + u
with  H=true health; X= socioeconomic variables; Z=objective health
measures; u=error term

I do not observe the true health, but only the self-assessed health
which includes a reporting error e, thus:
SAH = H + e
SAH = X*ß1 + Z*ß2 + v (with v=u+e)

I estimate the last equation via SEM the following way:
sem (age ->  sah) (education ->  sah) (blood ->  sah) (chronic ->  sah)
(limit ->  sah)

Then, I'm stuck - how do I get back to the first equation and model
the health indicator H? Also, can I estimate an ordered Probit model
in SEM?
I tried to use "SEM-Predictions", but I have the feeling that I need
to define a latent variable first in the SEM model. I'm totally new
with latent variable models - could it be that both the health index
and SAH are latent variables with the latter one being endogenous?

I hope that my problem is understandable. Any help will be very
appreciated, also some literature advice - thank you very much in
advance!

Samantha

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