Analysis of interlaboratory comparison when the measurements are not normally distributed

Laboratoire National de métrologie et d’Essais, 1 rue Gaston Boissier 75724 Paris Cedex 15, France

^* Corresponding author: alexandre.allard@lne.fr
^** Corresponding author: soraya.amarouche@lne.fr

Abstract

Testing laboratories are more and more concerned with the characterization of their measurement processes. In particular, the standard ISO 17025[2] requires the accredited laboratories to participate to interlaboratory comparisons to evaluate their proficiency to realize the measurement. Different statistical methods are available to exploit the results of this type of comparisons. In our study, first we have evaluated the reference value and the proficiency standard deviation with ISO 5725-2 standard [1] and in second part the calculation of statistical indicator Z-score with ISO13528 [5] standard to assess of proficiency of laboratory with the first estimated parameters. However, these statistical methods rely on the assumption that the measurement results are normally distributed. Based on measurements expressed in dBμV/m, which is a log transformation of an electric field level expressed in μV/m, this paper aims at the comparison between the statistical analysis of data expressed in the two different units and relates these results to the assumed statistical assumptions.