Nick, Jakob, Marc et al > Thanks for your helpful comments. I agree with you that any results that > are at a boundary should be discarded from the bootstrap distribution.
On the whole I the sentiments in this thread align with anecdotal findings from my experience. But, I was just wondering how you define your boundaries for variance and covariance parameters (e.g. OMEGA terms)? For variance terms, lower boundaries seems reasonably straightforward (e.g. 1E-5 seems close to zero). Upper boundaries are of course open, for the variance of a log-normal ETA would 1E+5 or 1E+4 be large enough to be considered close to a boundary? At what value would you discard the result? At what correlation value would you discard a result (>0.99, > 0.97...) as being close to 1. Clearly if this was for regulatory work you could define these a priori after having chosen any arbitrary cut-off. But the devil here lies with the non-regulatory work where you may not have defined these boundaries a priori. Steve -- Professor Stephen Duffull Chair of Clinical Pharmacy School of Pharmacy University of Otago PO Box 56 Dunedin New Zealand E: [email protected] P: +64 3 479 5044 F: +64 3 479 7034 W: http://pharmacy.otago.ac.nz/profiles/stephenduffull Design software: www.winpopt.com
