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/