Abstract

The report starts with an introduction into the Cusum quality control scheme. This scheme is meant to improve the operating characteristic in case of small samples. Therefore the likelihood ratios of some bad parameter value with respect to the good parameter value are being summed up for successive samples. It is shown how to extend the original one-sided univariate Cusum scheme into two-sided and multivariate schemes. A computer program is presented that can be used to fix the parameter values of the Cusum scheme. Finally, information is given on the application of the Cusum scheme within the BCR project for reference materials in water and food microbiology.