Re: st: Multiple correspondence analysis & PCA with ordinal variables

[Laura Gibbons <gibbonsl@u.washington.edu>]

Did you consider using -gllamm-?  I've not done this, but you could search 
for messages about IRT and gllamm.  Another alternative would be to call 
the R -ltm- package.

The other options I know of involve purchasing a separate program, like 
Mplus, Parscale, etc.

-Laura

On Thu, 13 May 2010, Owen Corrigan wrote:

> I am trying to extract a single index from a set of 7/8 ordinal
> variables measured over three categories (low, med, high). I
> understand that MCA (multiple correspondence analysis) is an analogue
> of PCA (principal components analysis) for categorical/ordinal data,
> and so have been using that in Stata 10. My concern is that I am not
> properly 'telling' Stata that the data is ordinal, and thus Stata may
> not be taking into account that category 3 > category 2 > category 1.
> I have read through the help file and options, but see no way to
> 'force ordinality' on the program; so I am worried that the analysis
> is merely treating each of the categories of the variables as
> independent, and not related.
>
> Is there a way to force ordinality? Should I be using a different method?
> All assistance greatly appreciated.
> Owen.
> *
> *   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/

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Laura E. Gibbons, PhD
General Internal Medicine, University of Washington
Box 359780, Harborview Medical Center, 325 Ninth Ave, Seattle, WA 98104
phone: 206-744-1842, fax: 206-744-9917, Office address: 401 Broadway, Suite 5122
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
*   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/