Bootstrap resampling!

From: "Iyer, Ganesh R [PRI]" <GIyer1@prius.jnj.com> Subject: Bootstrap resampling! Date: Fri, 23 Mar 2001 08:06:09 -0500 Dear NonMem Users This is something that came to my mind regarding Bootstrap procedures that we regularly perform to understand the stability and performance of the PK/PD model using Bootstrap approach. I had 30 subjects with both PK and PD data that I was trying to model and I was looking for stability and performance of my model stability. I was trying to perform model stability using Bootstrap (Thanks to Ruedi and Vladimir for providing me with the script file for S-plus!) to get a better feel for what the underlying distribution of my parameters really is. The bootstrap procedure that was followed was based on the sampling subjects at random but leaves each subject' concentration data unchanged. In one of the papers (JPB,1997) written by Ene Ette, He nicely quotes, " By resampling the original data with replacement, artificial samples are generated on which the inference of interest can be made as for the orginal sample. What we see is the subjects are replaced but the concentration from the original data set is taken by another subject, and the assumption is that our bootstrap data sets follows a similar distribution to the original data set. I am just wondering whether its a good idea to sample residuals at random rather than subjects, although the residuals depend on the concentration measurements? I would appreciate for your help on this topic. Many Thanks in Advance, Ganesh ------------------------------ Ganesh R. Iyer Clinical Pharmacokinetics and Pharmacology Dept RW Johnson Pharmaceutical Research Institute Raritan, New Jersey