On Wed, 22 Apr 2020 at 11:32, Sven Schreiber <svetosch@gmx.net> wrote:
Am 21.04.2020 um 21:54 schrieb robdans2@gmail.com:
> Thanks for the quick answer, what do you think would be a better fix? Changing the variable (for example making it a log)?

All I'm saying is that we're talking about an outlier that is going to
be removed. I know that this affects the test outcome of a diagnostic
test for heteroskedasticity, but it is still a different topic, most of
the time.

cheers
sven

Failure of your heteroskedasticity test can be regarded as indicating misspecification.  Have you done any other misspecification tests (e.g. autocorrelation, functional form, recursive residuals, etc.) and did any of these indicate misspecification?  Is your outlier the result of some policy change, innovation, change in method of compilation of your time series, or similar.  If so, you can use a point, or step dummy or another intervention variable to improve your model.   Even if you have heteroscedasticity your coefficient estimates are still consistent and you can use a robust estimate of their standard deviations.  What you do depends on your economic model, your data, and the aim of your analysis.

When Sven says 'whether that would be a proper "fix" '  I would think that he was referring to considerations such as the above.

John C Frain
3 Aranleigh Park

 
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