Re: advan8 vs. advan13 (CORRECTION)

Hi, Thanks to Peiming Ma and Thuy Vu for pointing out an error in my attempt to transform bioavailability into its logit. The logit transformation of a probability is ln(P/(1-P)) i.e. the log of the odds ratio. The reverse transform is correct i.e. exp(logit) is the odds ratio and P is then OR/(1+OR) (or 1/1+exp(-logit)). If THETA(1) is the bioavailability then this is (I hope) the correct transformation of THETA(1) and reverse transform to get the individual bioavailability with a random effect constrained to be within 0 and 1. MU_1=LOG(THETA(1)/(1-THETA(1)) ; logit of population bioavailability EXPP=MU_1+ETA(1) ; add random effect BIO=1/(1+EXP(-EXP(EXPP))) ; individual bioavailability Nick -- Nick Holford, Professor Clinical Pharmacology Dept Pharmacology & Clinical Pharmacology University of Auckland,85 Park Rd,Private Bag 92019,Auckland,New Zealand tel:+64(9)923-6730 fax:+64(9)373-7090 mobile:+64(21)46 23 53 email: [email protected] http://www.fmhs.auckland.ac.nz/sms/pharmacology/holford