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From   Felipe <Targa@umd.edu>
To   statalist@hsphsun2.harvard.edu
Date   Wed, 3 Aug 2005 22:03:31 -0400

I am estimating a system of equations simultaneously
determined (3 equations) with panel data using reg3 (3SLS
fixed effects). I=E2=80=99m interested in performing a test for; (i)
overidentifying restrictions and exogeneity; and (ii)
endogeneity. If my equation weren=E2=80=99t simultaneously
determined I wouldn=E2=80=99t have any problem using xtivreg, fe and
performing these tests with overidxt and hausman (equivalent
to ivendog).

>From Stata=E2=80=99s website it reads that =E2=80=9CHausman test in Stata
9.0 can be used to test for exogeneity or overidentifying
restrictions for two-stage least squares (2SLS) and three-
stage least squares (3SLS)=E2=80=9D. I would like to know if I can
perform a test (and how) for; (i) overidentifying
restrictions and exogeneity of the instruments in each of
the equations; and (ii) endogeneity of each of my endogenous
variables if, for example, I=E2=80=99m estimating the following
model:

reg3 (Y1 Y2 Y3 X1=E2=80=A6.Xn) (Y2 Y1 Y3 X1=E2=80=A6.Xn) (Y3 Y1 Y2 X1=E2=80=
=A6Xn)

If it is not with a Hausman test, are there other ways to
perform these tests after reg3?

It would be valid to perform these tests equation-by-
equation using xtivreg and then, if they don=E2=80=99t provide
enough evidence to reject the validity of the specification
and instruments, estimating the full system of equations
with reg3?

Thanks in anticipation,

Felipe

   _______________________________________
   Felipe Targa

   Ph.D. Candidate
   Dept of Civil & Environmental Engineering
   1173 Glenn Martin Hall
   University of Maryland, College Park MD 20742
   www.wam.umd.edu/~ftarga
   _______________________________________

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