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David Ross wrote:
> (...) Packages (like S+), coupled with the ubiquity of remarkable c=
omputing
>
> power, sometimes make it a bit *too* tempting to drop data into rob=
ust
> procedures. I'm guilty of this myself (especially since the robust=
ness
> of lmsreg is backed up by a beautiful geometric characterization). =
In
> anticipation of Doug Martin's response, let me offer (to anyone rea=
ding
> this thread) an example I sometimes give my students. Suppose your
> dataset has 2k+1 elements in it, k+1 of them take the value 0, and =
k of
> them take the value 100. The median is therefore 0. Now, change on=
e of
> the 0s into a 100. The median is now 100. This is robust?
>
Will the means at 100*k/(2k+1) and 100*(k+1)/(2k+1) best resume this =
data? I
don't think so.
This is not a problem of the median. There is no point looking for a =
center
mesure of a dichotomous variable !!!
Eva Cantoni
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