RE: posthoc step

From: "Steve Duffull" Subject: RE: [NMusers] posthoc step Date: Wed, December 8, 2004 3:19 pm Hi all Nick wrote: > When the SD for the prior on K was increased to 9 then Khat changes abruptly from 10 to 0.94. I am not going to attempt to comment meaningfully on the findings to date - but want to ask another question about the findings. If the prior for K is N(10,x) and the data were computed based on K_i=1 then how could NONMEM (or SAS...) have computed a Khat of < 1? I would have guessed that the Bayesian solution would have wanted the value of Khat: 1 < Khat < 10. That Khat was 0.94 would indicate that the prior would have to be noninformative, and therefore a value of Khat < 1 is simply due to some estimation bias in the system. I would have guessed that a N(10,x), where x lies between 4 and 10 is not noninformative. So - why is this happening? It is of course possible that the solution is obvious and I have missed part of the previous thread which explains why this is so - in which case just ignore this email. 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