dear all,
sorry for arriving late - been busy marking (appalling) exams and
projects over the last few days.
Coming to the issue, I confess I fail to see the point of resampling
without replacement.
As far as the bootstrap is concerned, as far as I know resampling MUST
be carried out with replacement. This was clearly stated at the outset
of the literature (eg in Efron-Tibshirani's 1993 book "with replacement"
is in italics the first time the resampling algorithm is described, at
p. 45). The rationale is that our aim is to generate artificial data
distributed as a multinomial given by the empirical distribution
function of the data. Note this holds for each artificial datapoint.
What happens if use resampling without replacement? the various
artificial datapoints would be generated with different multinomials.
Further, we consider this: if the bootstrap pseudodataset is of the same
size of the original dataset (as typical, although by no means
necessary) resampling with no replacement we end up with the original data!
bye,
Stefano
--
________________________________________________________________________
Stefano Fachin
Professore Ordinario di Statistica Economica
Dip. di Scienze Statistiche
"Sapienza" Università di Roma
P.le A. Moro 5 - 00185 Roma - Italia
Tel. +39-06-49910834
fax +39-06-49910072
web
http://stefanofachin.site.uniroma1.it/