Am 21.12.2020 um 13:17 schrieb Artur Bala:
Hi,
Not sure if this is a gretl issue or an econometric one actually.
I'm trying to come up with a script that replicates Stata's "rreg"
command which is basically a robust estimation for outliers
correction. It is based on an iterative WLS resulting in an optimal
weight vector.
Now, for testing purposes, I'm running OLS and WLS models
successively. I note that the WLS' "Statistics based on the original
data" SSR and S.E of regression are slightly different from the
respective OLS' output (*in bold *below). Should these parts of
outputs be the same?
If not, hhat is the difference coming from ?
Well, it should be the different estimators, no? If I understand the
output correctly, WLS reports what's the outcome if the unweighted data
are used, but the coefficient values from WLS are applied, in order to
have a meaningful comparison with the OLS results. And if there were no
difference, WLS wouldn't have made any difference.
cheers
sven