st: Testing for rho differences after mvprobit

[<S.Jenkins@lse.ac.uk>]

------------------------------

Date: Fri, 8 Apr 2011 00:47:20 +0200
From: =?iso-8859-1?Q?Jaime_G=F3mez?= <jaime.gomez@unizar.es>
Subject: st: Testing for rho differences after mvprobit

Dear Statalisters
I have estimated a model through the "mvprobit" command of Capellari and Jenkins. I would like to test whether the differences in the rhos are statistically significant. For example, I would like to know whether rho21 is different from rho31 or whether rho21>rho42. Is there any way of doing this with Stata?
Thank you very much.
Jaime Gómez.
================

-mvprobit- is available on SSC (this is a later version than the 2003 Stata Journal version). [Remember the Statalist FAQ reminding you to say where modules are available from.]

You can straightforwardly test equality of correlations using -test- but referring to the ("atrho") transformed versions of the correlations rather than the correlations themselves. Look in e(V) and e(b) using -matrix list- for the names used by the program. Inequality constraints cannot currently be tested directly, as far as I know.

If you have 4 outcome variables, then you might find the Cappellari/Jenkins material in Stata Journal 6(2) 2006 (downloadable from SJ website) of interest -- using code of the kind illustrated there together with the plugin will estimate your model faster. That's relevant if you're having to fit it multiple times.  See also -cmp- on SSC by David Roodman.

Stephen
-------------------------------------
Professor Stephen P. Jenkins  <s.jenkins@lse.ac.uk>
Department of Social Policy and STICERD
London School of Economics and Political Science
Houghton Street, London WC2A 2AE, U.K.
Tel. +44 (0)20 7955 6527
Survival Analysis using Stata: http://www.iser.essex.ac.uk/survival-analysis
Downloadable papers and software: http://ideas.repec.org/e/pje7.html


Please access the attached hyperlink for an important electronic communications disclaimer: http://lse.ac.uk/emailDisclaimer

*
*   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/