Obtaining gradients for the computation of prediction intervals

From:Michael.J.Fossler@gsk.com Subject:[NMusers] Obtaining gradients for the computation of prediction intervals Date:11:38 AM 9/17/02 -0400 Hi everyone; Aarons et al. (Br J Clin Pharmacol (1989) 28:305)) describes a method of calculating a prediction interval for assessing how well a model predicts a validation data set. He first computes a standardized prediction error for each concentration (SPE) which is SPE=Observed-Predicted/SD(Observed) the SD(Observed) is obtained using the following expression (inserted as a graphic) Can anyone tell us how to obtain the partial derivatives (gradients) which we need to compute this standard deviation? Thanks, Mike Fossler, Clinical PK, Modeling & Simulation Jagadeesh Aluri, PK Operations GlaxoSmithKline