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Re: st: cfa1: How to obtain standardized coefficients?


From   Bryan Chung <bryanc.dal@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: cfa1: How to obtain standardized coefficients?
Date   Thu, 29 Apr 2010 15:57:27 -0300

My apologies, I did not know cfa1 was an older "version" of confa.

I am sorry for the repetitive nature of this question, but is the method to calculate the standarded loadings for confa the same then? Or is there a canned way in confa that does this?

Bryan

On Apr 29, 2010, at 3:40 PM, Stas Kolenikov wrote:

> There is no canned way to generate the standardized coefficients. You
> can obtain the necessary results with -nlcom-. You need to multiply
> the loading by the standard deviation of the latent variable, and
> divide by the standard deviation of the indicator. In fact, these are
> the square roots of the reported R-squares for the simple one-factor
> model that -cfa1- fits.
> 
> clear
> set obs 100
> set seed 12345
> gen f = rnormal()
> gen x1 = f + 0.5*rnormal()
> gen x2 = 1.2*f + 0.7*rnormal()
> gen x3 = 1.5*f + rnormal()
> cfa1 x*
> nlcom _b[x1:_cons]*sqrt(_b[phi:_cons]
> /(_b[x1:_cons]*_b[x1:_cons]*_b[phi:_cons] + _b[x1_v:_cons]))
> nlcom _b[x2:_cons]*sqrt(_b[phi:_cons]
> /(_b[x2:_cons]*_b[x2:_cons]*_b[phi:_cons] + _b[x2_v:_cons]))
> nlcom _b[x3:_cons]*sqrt(_b[phi:_cons]
> /(_b[x3:_cons]*_b[x3:_cons]*_b[phi:_cons] + _b[x3_v:_cons]))
> 
> If you like, you can combine the three -nlcom-s into a single one:
> 
> nlcom ( stlambda1: _b[x1:_cons]*sqrt(_b[phi:_cons] / ( _b[x1:_cons] *
> _b[x1:_cons] * _b[phi:_cons] + _b[x1_v:_cons])) ) ( stlambda2:
> _b[x2:_cons]*sqrt(_b[phi:_cons] / ( _b[x2:_cons] * _b[x2:_cons] *
> _b[phi:_cons] + _b[x2_v:_cons])) ) ( stlambda3: _b[x3:_cons] * sqrt(
> _b[phi:_cons] /(_b[x3:_cons] * _b[x3:_cons] * _b[phi:_cons] +
> _b[x3_v:_cons])) )
> 
> I COULD consider providing the standardized loadings for the more
> recent -confa- package (that's also better documented, see
> http://www.stata-journal.com/article.html?article=st0169). I don't
> really support and develop -cfa1- anymore.
> 
> On Thu, Apr 29, 2010 at 1:16 PM, Bryan Chung <bryanc.dal@gmail.com> wrote:
>> I'm currently performing a confirmatory factor analysis on a questionnaire in which each item in the questionnaire is supposed to correspond to a single factor. I am also trying to figure out whether further item reduction can be performed (the original factor analysis that reduced the generated items to the existing questionnaire has never been replicated or verified and the questionnaire is quite lengthy!).
>> 
>> I understand that there is a somewhat arbitrary cutoff of 0.3 for a standardized coefficient in a CFA to drop an item, but am at somewhat of a loss as to how to generate these standardized coefficients with the cfa1 command.
> 
> -- 
> Stas Kolenikov, also found at http://stas.kolenikov.name
> Small print: I use this email account for mailing lists only.
> 
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