RE: PK models for rich and sparse sampling

From: Steve Duffull sduffull@pharmacy.uq.edu.au Subject: RE: [NMusers] PK models for rich and sparse sampling Date: Tue, 1 Jun 2004 09:41:51 +1000 Hi Mark When you used informative priors as indicated below (and in previous threads): >Another option is the PRIOR method. How do you set up your prior on your between-subject variance? I am guessing that NONMEM uses an inverse Wishart for the prior on OMEGA, which means that you will need to specify your degrees of freedom in some manner. Since you only have your dense data as your "prior" then you will not have enough information to determine the uncertainty in your omega estimate (unless you use your SE's here which is likely to be risky due to assumed normality). If you do use your SE's then how do you go about figuring out your dof (?), unfortunately the Wishart is annoyingly tricky and there is not a linear relationship between dof and inverse precision. Regards Steve ========================================= Stephen Duffull School of Pharmacy University of Queensland Brisbane 4072 Australia Tel +61 7 3365 8808 Fax +61 7 3365 1688 University Provider Number: 00025B Email: sduffull@pharmacy.uq.edu.au www: http://www.uq.edu.au/pharmacy/sduffull/duffull.htm PFIM: http://www.uq.edu.au/pharmacy/sduffull/pfim.htm MCMC PK example: http://www.uq.edu.au/pharmacy/sduffull/MCMC_eg.htm