Validation of the performance of process stream analyzer systems with nonparametric behavior

Literature describes several procedures based on statistical principles to validate whether the degree of agreement between the results produced by a stream analyzer system—systems for determining chemical and physical characteristics by continual sampling, automatic analysis, and recording or otherwise signaling of output data—and those produced by an independent test measurement procedure, which purports to measure the same property, meets user-specified requirements. However, these documents always consider that the data gathered during validation procedure are normally distributed, and this supposition it is not always true. The aim of this manuscript is to develop four different procedures applied to data with nonparametric behavior. The most representative validation procedure compares measures of position and dispersion, using typical process samples, while the less representative one compares only measures of position, using a reference sample. These nonparametric data are also treated using parametric statistics for comparison. The results show that different conclusions can be reached when the nonparametric data are treated as parametric. A new Brazilian standard is being carried out based on this subject, in order to complement the international standards.