Christine,
This comes up from time to time on Statalist.
Here's an explanation of the problem:
http://www.stata.com/statalist/archive/2004-08/msg00246.html
One solution is to use an artificial-regression version of the Hausman test
for tests of specific regressors. See Wooldridge, Econometric Analysis of
Cross-Section and Panel Data (2002), p. 90.
Cheers,
Mark
Quoting Christine Lee <[email protected]>:
> Hi
>
> I ran a hausman test between fixed and random effects models and got
> the
> message (V_b-V_B is not positive definite) at the end of the
> estimation.
>
> Has anyone got a clue what this is and ways of resolving this?
>
> Thanks
> Christine Lee
>
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>
Prof. Mark Schaffer
Director, CERT
Department of Economics
School of Management & Languages
Heriot-Watt University, Edinburgh EH14 4AS
tel +44-131-451-3494 / fax +44-131-451-3294
email: [email protected]
web: http://www.sml.hw.ac.uk/ecomes
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