Re: st: fixed effects regression

[David Jacobs <jacobs.184@sociology.osu.edu>]

If you use the stata commands "xtreg" or "areg" --or the other fixed 
effects commands for limited dependent variables--you can't control 
the number of fixed effects; these programs do this automatically.

If you alter an OLS analysis by including dummies for each case (and 
possibly dummies for each period), such models will run, although the 
program may suppress one case dummy or a year dummy or the 
intercept.  If you use this augmented OLS approach to estimate a 
fixed-effects model, the "reg" program will list the coefficients on 
the dummies and their standard errors.  The only disadvantage is 
output that can be quite large.

Note that throwing in the dummies in an attempt to use a fixed 
effects approach to explain limited dependent variables with 
estimators such as logit, probit, or Tobit will produce incorrect 
estimates. This dummy variable inclusion approach only is sound for 
an analysis that could appropriately use stata routines such as 
"xtreg" or "areg".

Dave Jacobs

At 04:28 PM 9/30/2005, you wrote:

> hi, if I am running a regression with fixed effects. (1) is there a 
> limit on the number of fixed-effects I can use, and (2) is there a 
> way to retrieve the coefficients on the fixed effects (and possibly 
> also their standard errors) afterwards?
> Thank you
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