Estimating the uncertainty of binary test results to assess their compliance with regulatory limits

A procedure to calculate the uncertainty associated to a binary response, of the type yes/no, originated from an instrumental screening system, is described. Useful equations have been developed based on statistical intervals, and their validation were performed with standard commercial solution. It was applied to a differential pulse anodic stripping voltammetry (DPASV) screening system to analyse tap water, specifically, for determining Pb2+ and Cd2+ above the UE legislation limits, 10 and 5 mug/l, respectively. A cut-off value from the responses of the calibration samples is calculated and compared with the responses obtained for unknown samples. From this comparison, we will be able to take a compliance yes/no decision, with an alpha probability of committing a type I error. Another parameter, r(screening), is calculated in order to compare different methods for the same screening application. (C) 2002 Elsevier Science B.V. All rights reserved.