A statistical model for inspection procedures in forensic and environmental analysis

Legal regulations on composition and safety of food products require inspeetion programs to maintain the decisions or to get insight in the real situation. Such programs consist of a sampling procedure followed by analysis of the samples. In monitoring of environmental contamination similar programs are required. When large quantities of samples for monitoring of contaminants in environment or in food chains have to be analysed, and the majority of the samples fulfills the legal requirements, a two stage control system will be attractive. In the first stage samples are analysed by a simple 'screening method', to sift out the large number of samples fulfilling the requirements ('negative result'). The minor part of samples not fulfilling the requirernents ('positive result') are further investigated by a sophisticated 'confirrnatory method', specific tor the analyte(s) of interest, for an uitimate judgement. For this kind of inspeetion a simple model is used in this study, in order to calculate the fraction of false negative results in the inspection