Honest measurements

Mats Karlsson wrote: << Chemists, however pushed, would never report negative concentrations, not for past studies, not for future studies. The methods they use don't even report them.>> I am working with a chemist using LC/MS who has been persuaded to look honestly at his data without preconceived ideas of limits of quantitation and detection. Indeed when he opened his eyes he found that his system was indeed giving negative concentration measurements (at times when concentrations were expected to be very low). Of course we must do other things when the data is censored by bad scientific practice in the chemist's lab but with honest measurments an additive residual error model is required. Nick -- Nick Holford, Professor Clinical Pharmacology Dept Pharmacology & Clinical Pharmacology University of Auckland, 85 Park Rd, Private Bag 92019, Auckland, New Zealand [email protected] tel:+64(9)923-6730 fax:+64(9)373-7090 mobile: +64 21 46 23 53 http://www.fmhs.auckland.ac.nz/sms/pharmacology/holford