Re: Minimization Terminated in Bootstrapping

On 30 October 2014 21:17, siwei Dai <[email protected]> wrote: > Hi, Dr. Bonate: > > Thank you very much for your comments. There are some more sparse data in > the data set and I wasn't aware that I should do stratification for > bootstrapping, so thank you for pointing it out. > > Best regards, > > Siwei > > On Wed, Oct 29, 2014 at 11:58 AM, Bonate, Peter <[email protected] > > wrote: > >> Not just yet. I’ve seen many people just naively bootstrap their >> dataset. It may be that your bootstrap datasets do not adequately >> represent model development dataset. For example suppose you had 75% >> sparse data and 25% rich data in your model development set. It is >> imperative that your bootstrap dataset maintain this ratio so you need to >> stratify by data richness. Otherwise you could get a bootstrap dataset that >> is predominantly sparse data which would not support such a complicated >> absorption model. The same holds true if there are important covariates in >> your model. >> >> >> >> pete >> >> >> >> >> >> Peter L. Bonate, PhD >> >> Senior Director >> >> Global Head - Pharmacokinetics, Modeling, and Simulation >> >> Global Clinical Pharmacology & Exploratory Development >> >> >> >> Astellas >> >> 1 Astellas Way, 2N.184 >> >> Northbrook, Il 60062 >> >> phone: 224-205-5855 >> >> fax: 224-205-5914 >> >> email: [email protected] >> >> >> >> >> >> *From:* [email protected] [mailto:[email protected]] >> *On Behalf Of *siwei Dai >> *Sent:* Tuesday, October 28, 2014 9:00 AM >> *To:* [email protected] >> *Subject:* [NMusers] Minimization Terminated in Bootstrapping >> >> >> >> Dear NM users: >> >> >> >> I have a data set where the absorption phase is highly variable. A >> complicated absorption model (the TRANSIT model) significantly improve the >> model fit (OFV drops over 250) compared to a 1st-order absorption model >> with lag time. The complicated final model converged and the covariance >> step was successful. The condition number is low (less than 10), although >> there were many runs with rounding errors during model development. >> >> >> >> However, in the bootstrap analysis,about 600 out of 1000 iterations had >> minimization terminated which leads to a successful rate of only 40%. >> >> >> >> My question is: is there any consensus regarding the acceptable >> successful rate for bootstrap analysis? I understand 40% is very low. >> Should I reject this model then? >> >> >> >> Any suggestions will be greatly appreciated. >> >> >> Thanks, >> >> >> >> Siwei >> > >