RE: st: Adjustment to likehood value due to dependence of data observations

[Cameron McIntosh <cnm100@hotmail.com>]

Memon,
On Nick's second point, see:
Freedman, D.A. (2006). On the So-Called “Huber Sandwich Estimator” and “Robust Standard Errors”. The American Statistician, 60(4),  299-302. http://www.stat.berkeley.edu/~census/mlesan.pdf
Why bother getting robust estimates of standard errors for a potentially biased estimates in a misspecified model?
Cam
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> Date: Thu, 22 Sep 2011 15:30:05 +0100
> Subject: Re: st: Adjustment to likehood value due to dependence of data observations
> From: njcoxstata@gmail.com
> To: statalist@hsphsun2.harvard.edu
>
> #1 is easier. The answer is No in general. If you have time series for
> panels, you need to fit appropriate models at the outset. That is the
> principle. If you ignore that, then in broad terms, your parameter
> estimates may sometimes be about right, but standard errors are likely
> to be wrong and P-values are likely to be very very wrong. However, if
> the model really is wrong, it is best to fit another.
>
> #2 I don't understand. If there is a trend in residuals then your
> model sounds misspecified. Getting a better idea of what the standard
> errors are, or should be, for a model you have fitted that is
> evidently wrong doesn't sound very useful. You may be misunderstanding
> what -robust- options do, which is much less than people often think.
>
> On Thu, Sep 22, 2011 at 3:10 PM, Abdul Q Memon <a.memon@ucl.ac.uk> wrote:
>
> > I would really appreciate your reply on this.
> >
> > I have run several models using glm (possion and negative binomial)
> > command in STATA. Based on the log-likelihood and BIC values I have
> > selected the most appropriate models (with smallest BIC values). After
> > this I have run GEE with AR1 structure for only the preferred model to
> > account for serial correlation in data. I have these two questions.
> >
> > 1. Since my model seclection is based on (log-likelihood and BIC values)
> > and in this case data is not independent (time series and panel data), is
> > there a way in stata to adjust the likelihood after running glm command if
> > the data is not independent.
> >
> > 2. After running gee command still there is some trend in residuals. Do i
> > need to run robust command to adjust standard errors after gee?? my
> > understanding is robust command is for corrections to standard error after
> > OLS.
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