Yes, agreed. Many thanks for the reference and the comments.
Vidya
>>> [email protected] 12/04/03 01:14pm >>>
You indicated later that you had solved
the question of how to do this in Stata.
Irrespective of that, the t test is based
on the assumption that observations
are independent, which in most panel
situations seems unlikely; otherwise,
your P-values are seriously inaccurate.
That doesn't make analysis impossible, but it does mean
that the autocorrelation is needed to
interpret the t test properly.
Among many other sources, Rupert G.
Miller's "Beyond ANOVA" is good on
this kind of problem.
Nick
[email protected]
Vidya Mahambare
> I am having some problem using ttest. I have a panel data -
> 10 time periods,
> 2000+ firms from 13 sectors and 3 ownership categories.
> I am interested in testing whether the means of a variable
> (efficiency
> indicator) are different for the ownership pairs during a
> particular time period
> for each sector.
> Eg; time = 1 to 4, ttest efficiency if owner =1 and owner
> =3 for sector 1, then
> sector 2 and so on
> Time = 5 to 8, ttest efficiency if owner =1 and owner =3
> for sector 1, then
> sector 2 and so on
>
> Should I temporality drop observations in all sectors
> except one and then do
> ttest? I have tried several different ways, but without success.
>
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