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From |
<Seyi.Soremekun@lshtm.ac.uk> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
Re: st: calculate alpha after polychoric factor analysis |

Date |
Mon, 13 Feb 2012 15:18:18 +0000 |

Thanks (and for the polychoric command itself). The sample size is not an issue - all respondents answered all the questions, displaying -n- was just a check for me (if that is what you meant in your note?) I'm not sure about the appropriateness of using alpha either, however, I know that ordinal alphas are available in other types of software (Basto and Pereira 2012 J. Statistical Software 46(4)), and wondered if there was something I could use in Stata. I was hoping that I could ask stata to calculate the alpha on the saved matrix rather than a list of variables. Seyi >>> Stas Kolenikov <skolenik@gmail.com> 13/02/2012 14:34 >>> I am not sure -alpha- is entirely appropriate in this situation. Tenko Raykov published a number of papers in late 1990s conceptualizing composite reliability extending the alpha to more general situations of factor analysis. I don't know if any of that is implemented as a third party package. Obviously, this is doable as -nlcom- following -sem- or -confa-, although you would need to spend some time figuring out how to best use either the estimated coefficients or the resulting matrices. Note also that -polychoric- computes correlations in pairwise fashion, so there may be no single sample size that is suitable for factor analysis (although this is probably just a scaling coefficient somewhere, as the eigenvalues and eigenvectors produced in factor analysis do not depend on -n-). On Mon, Feb 13, 2012 at 8:54 AM, <Seyi.Soremekun@lshtm.ac.uk> wrote: > Dear Stata Listers, > > I would like to estimate the equivalent of Cronbach's alpha after factor analysis conducted on a polychoric matrix of ordinal, Likert items. I started out in a pretty standard way thus: > > polychoric var1 - var29 > display r(sum_w) // check number of respondents answered all = 331 > matrix r = r(R) > factormat r, n(331) factors(3) ipf > alpha? > > Is there such functionality available, or might I have to re-do the whole analysis in R or SAS? > > thanks, > > Seyi > > > Dr Seyi Soremekun > Faculty of Epidemiology and Public Health > London School of Hygiene and Tropical Medicine > London WC1E 7HT > +442079272464 > > > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/statalist/faq > * http://www.ats.ucla.edu/stat/stata/ -- Stas Kolenikov, also found at http://stas.kolenikov.name Small print: I use this email account for mailing lists only. * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/ * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**Re: st: calculate alpha after polychoric factor analysis***From:*"Joseph Coveney" <jcoveney@bigplanet.com>

**References**:**st: calculate alpha after polychoric factor analysis***From:*<Seyi.Soremekun@lshtm.ac.uk>

**Re: st: calculate alpha after polychoric factor analysis***From:*Stas Kolenikov <skolenik@gmail.com>

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