Hi Elena,
VPCs are accurately called prediction intervals not confidence intervals. The difference is that a prediction interval shows what you would expect for the next individual in a study while a confidence interval shows what you would expect for the result of a statistic (often confidence intervals of a mean are shown). With many VPCs, the confidence interval of the median and the confidence interval of the 5th and 95th percentiles are shown. Also, when the lines indicate the median, 5th, and 95th percentiles of the simulations, that is the 90% prediction interval since it is the middle 90% of the data (not the 95% confidence interval). Thanks, Bill *From:* owner-nmus...@globomaxnm.com <owner-nmus...@globomaxnm.com> *On Behalf Of *Soto, Elena *Sent:* Thursday, March 14, 2019 12:49 PM *To:* nmusers@globomaxnm.com *Subject:* [NMusers] VPCs confidence intervals? Dear all, I have a question regarding visual predictive checks (VPCs). Most of VPCs used now, include a line representing the median and 5th and 95 th percentiles of the data values and an area around the same percentiles that is commonly define as the 95% confidence interval (of the simulations). But is it correct, from the statistical point of view, to call confidence interval to this area? And if this is not the case how should we define them? Thanks, Elena Soto Elena Soto, PhD Pharmacometrician Pharmacometrics, Global Clinical Pharmacology Global Product Development *Pfizer R&D UK Limited, IPC 096* *CT13 9NJ**, Sandwich, **UK* *Phone : +44 1304 644883* ------------------------------ Unless expressly stated otherwise, this message is confidential and may be privileged. It is intended for the addressee(s) only. Access to this e-mail by anyone else is unauthorised. If you are not an addressee, any disclosure or copying of the contents of this e-mail or any action taken (or not taken) in reliance on it is unauthorised and may be unlawful. If you are not an addressee, please inform the sender immediately. Pfizer R&D UK Limited is registered in England under No. 11439437 with its registered office at Ramsgate Road, Sandwich, Kent CT13 9NJ
