Doh! I should've thought of that. You're right of course. If I run a model dropping experience altogether, and instrument for ed76, smsa76 and south76, the Hausman test has df = 3.
I'm still confused about the 0.0 critical values in the weak instruments test though... PS -----Original Message----- From: gretl-users-bounces(a)lists.wfu.edu [mailto:gretl-users-bounces(a)lists.wfu.edu] On Behalf Of Allin Cottrell Sent: Wednesday, April 21, 2010 2:14 PM To: Gretl list Subject: Re: [Gretl-users] tsls tests On Wed, 21 Apr 2010, Allin Cottrell wrote: > On Wed, 21 Apr 2010, Summers, Peter wrote: > > > I'm still not sure about the df in the Hausman test though. In > > the last model it seems to me that this should be 2, not 1... > > I will take another look at that. You still have perfect collinearity in the relevant respect. The issue is that in the Verbeek schooling dataset the experience values are "fake" (as is quite often the case in labor-market datasets); they are calculated numbers representing "potential experience", as in exp76 = age76 - ed76 - 6 This means that when you run the unrestricted regression for the Hausman test one of the "hat"-variables gets dropped automatically, leaving just one degree of freedom for the test. Allin _______________________________________________ Gretl-users mailing list Gretl-users(a)lists.wfu.edu http://lists.wfu.edu/mailman/listinfo/gretl-users
