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Re: st: SEM with categorical variables


From   Stas Kolenikov <skolenik@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: SEM with categorical variables
Date   Tue, 28 Aug 2012 12:37:49 -0500

So do you know exactly what Mplus does? Having the software decide for
you what to do is good for exploratory phases, but for real research,
you have to know what you are doing, and make sure the suggested
default is appropriate for your analysis.

Incidentally, I've been doing some polychoric-to-sem work earlier
yesterday. Here's the outline:

local thevars <varlist of the variables of interest>
polychoric `thevars'
mat polychR = r(R)
forvalues i=1/`: word count `thevars' ' {
  forvalues j=1/`i' {
    local setcor `setcor' `=polychR[`i',`j']'
  }
  if `i' < `: word count `thevars' ' local setcor `setcor' \
}
local N = _N
clear
ssd init `thevars'
ssd set obs `N'
ssd set cor `setcor'
sem ( your model structure comes here)

Not terribly elegant, but that's way better than nothing. (Don't
assume this will work as a black box; you would be much better off
understanding what each line does.)

On Tue, Aug 28, 2012 at 3:41 AM, Duru <duru80@gmail.com> wrote:
> Dear all,
> I am trying to estimate a structural equations model with Stata 12. I
> have ordinal items for my latent dependent variable and categorical
> manifest independent variables.
> I am not clear on how to handle this. I have read somewhere on the web
> that estimating polychoric correlations and feeding them into SEM
> could be an option or specifying another estimation method (than ML)
> would suffice? In Mplus I just need to specify those variables as
> categorical and it chooses the proper method by default.
>
> Many thanks,
>
> Duru
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-- 
-- Stas Kolenikov  ::  http://stas.kolenikov.name
-- Senior Survey Statistician, Abt SRBI  ::  work email kolenikovs at
srbi dot com
-- Opinions stated in this email are mine only, and do not reflect the
position of my employer
*
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*   http://www.ats.ucla.edu/stat/stata/


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