Bookmark and Share

Notice: On March 31, it was announced that Statalist is moving from an email list to a forum. The old list will shut down on April 23, and its replacement, statalist.org is already up and running.


[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

RE: st: Panel mixed-effects models


From   "Downey, Patrick" <PDowney@urban.org>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: Panel mixed-effects models
Date   Thu, 8 Mar 2012 13:13:54 -0500

Hi David,

Thanks for your response. As you suggested, I misspoke. I meant that I
expect the individual effects to be correlated with the covariates (X), as
you said, which violates the assumptions required for random individual
effects.

I agree with you that it is a bit odd to have random slopes and fixed
intercepts, but I can't think of anything that would be wrong with it. It
feels strange, but I haven't found any reason why it shouldn't be possible.

-Mitch

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of David Hoaglin
Sent: Thursday, March 08, 2012 1:04 PM
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: Panel mixed-effects models

The random-effects model does not assume absence of correlation between
individual effects (e.g., random intercepts) and Y.  Indeed, such effects
are often the main source of the correlation structure for Y.  Did you have
in mind the assumption that the random effects are not correlated with the
covariates (here, X_it)?  It seems a little odd to have random slopes but
fixed intercepts.

David Hoaglin

On Thu, Mar 8, 2012 at 12:12 PM, Downey, Patrick <PDowney@urban.org> wrote:
> Hello,
>
> I am trying to estimate a panel model of the form:
> Y_it = a_i + a_t + B_i * X_it + e_it
>
> I would like to use fixed effects for both of the 'a' coefficients 
> because I believe that the individual-effects are correlated with Y 
> (so the assumptions for random effects are not met). That would be a 
> simple two-way fixed effects model. However, I would like to use 
> random effects for the B coefficient. Thus, I want to assume B_i = B + 
> n_i, where n_i is a normally distributed random variable.
>
> I cannot figure out how to estimate this model in Stata. It seems that 
> xtmixed should be able to handle it, but with large N or large T, I 
> think there are complications. I couldn't find examples (for xtmixed 
> or xtrc) that use fixed effects for individual- or time- effects but 
> random slope coefficients, although I think this is possible.
*
*   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/


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