This came up several months ago on the list but I am still confused: As a
means for dealing with outliers, what are the relative merits of -rreg- and
-qreg-? When should one be preferred over the other?
As I understand it, -rreg- goes through this complicated weighting scheme,
which causes outliers to be weighted less heavily. -qreg- (by default)
does median regression, and the median is less affected by outliers than
the mean is.
In terms of giving a quick 30 second intuitive explanation, I like
-qreg-. On the other hand, in the few examples I've tried myself or seen
elsewhere, the results from -rreg- seemed more plausible. On the other
other hand, in those examples -rreg- basically just dropped the extreme
outliers, and I could do that myself without a fancy program.
This is one of the problems with using Stata in a stats class. When I only
used SPSS, these issues never came up, because as far as I can tell SPSS
can't do anything like this!
