Efficacy of robust analysis of variance for the interpretation of data from collaborative trials

Abstract

The Analytical Methods Committee (AMC) robust analysis of variance method has been compared with the Harmonized Protocol for the interpretation of data from collaborative trials. Many data sets, representing the extremes of concentration and precision, have been selected from published studies and subjected to the two methods for calculating estimates of the mean and the variances of repeatability and reproducibility. In addition the variabilities of the statistics have been investigated by the bootstrap method. The conclusion is that the AMC robust procedure is considerably more reliable than the Harmonized Protocol. Although the two methods give quite close results generally, the variability of the estimates produced by the Harmonized Protocol is considerably greater because of the masking of outliers. Even the robust method gives estimates that are more variable than expectations based on normal distribution theory.