Statalist


[Date Prev][Date Next][Thread Prev][Thread Next][Date index][Thread index]

st: re: prob with xttest2


From   Kit Baum <baum@bc.edu>
To   statalist@hsphsun2.harvard.edu
Subject   st: re: prob with xttest2
Date   Sun, 2 Sep 2007 11:11:51 -0400

Abhijit reports

the xttest2 command for cross-sectional correlation is generating the
following reply

Correlation matrix of residuals is singular.
not possible with test
r(131);



The xttest2 command is looking at the correlation matrix of the residuals, which is N x N, where there are N groups of T observations in the panel. Abhijit says "in my case N=85, T=8." The rank of that correlation matrix thus cannot exceed 8 (by definition, there can be no more than 8 linearly independent vectors in the 85 x 85 matrix). As in the case of -sureg-, which uses this correlation matrix in the "Zellner step", the test cannot be performed for panels with N > T.


Kit Baum, Boston College Economics and DIW Berlin
http://ideas.repec.org/e/pba1.html
An Introduction to Modern Econometrics Using Stata:
http://www.stata-press.com/books/imeus.html


*
* For searches and help try:
* http://www.stata.com/support/faqs/res/findit.html
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/




© Copyright 1996–2014 StataCorp LP   |   Terms of use   |   Privacy   |   Contact us   |   What's new   |   Site index