Re: Re: FO vs FOCE vs LAPLACIAN

From: Nick Holford <n.holford@auckland.ac.nz> Subject: Re: [NMusers] Re: FO vs FOCE vs LAPLACIAN Date: Wed, 16 Jul 2003 13:50:48 +1200 S nmusers@globomaxnm.com Raj, IMHO FO should usually be avoided. Its approximations are known to be worse than FOCE. FOCE also has its problems but they may not be as bad. I think the myth about FO being suitable for sparse data has arisen because when you sparse data you can learn very little and it therefore hard to be mislead too far by FO. The LAPLACIAN option is probably preferable over simple FOCE because it works harder at getting what should be the right answer. Don't sweat about $COV. The output is hardly worth the electrons used to generate it. There is no evidence that I know of that getting $COV to run is a reliable sign of a better model. My experience has often been the opposite. Often only crummy and naively simple models run with $COV and more sensible models which clearly fit the data better (based on eyeball tests of predictions matching observations) will fall over with the kind of error you report below. Nick -- Nick Holford, Dept Pharmacology & Clinical Pharmacology University of Auckland, 85 Park Rd, Private Bag 92019, Auckland, New Zealand email:n.holford@auckland.ac.nz tel:+64(9)373-7599x86730 fax:373-7556 http://www.health.auckland.ac.nz/pharmacology/staff/nholford/