I have encountered the same problem and it appears that this has something to do with the fixed effects model being a conditional logit. I would be very interested in knowing myself what the answer is.
>>> [email protected] 10/31/02 02:22PM >>>
I am running a series of analyses using xtlogit. In order to identify
which method of xtlogit is appropriate, I am using the Hausman test with
xtlogit, fe run first, then xtlogit, re run second. On occasion, I run
into the problem where the Hausman test produces an assumption error
indicating the following:
Test: Ho: difference in coefficients not systematic
chi2( 1) = (b-B)'[(V_b-V_B)^(-1)](b-B)
= -0.80 chi2<0 ==> model estimated on
these
data fails to meet the
asymptotic
assumptions of the Hausman test
I was earlier advised to eliminate the cases dropped by the fixed
effects model (due to lack of variation in the dependent variable) for
both analyses, but that did not change the error problem.
Does anyone have any ideas?
Thanks in advance,
Marie
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