Degrees of Equivalence in a Key Comparison

TL;DR

This paper discusses measurement models for interlaboratory key comparisons, incorporating a new concept of multiple true values for standards, and confirms the systematic laboratory-effects model remains appropriate under this new framework.

Contribution

It introduces measurement models based on the 2008 VIM revision, considering multiple true values, and validates the continued relevance of the systematic laboratory-effects model.

Findings

Systematic laboratory-effects model remains valid with multiple true values.

New measurement models incorporate the 2008 VIM concept of multiple true values.

Analysis confirms the model's robustness under revised measurement standards.

Abstract

In an interlaboratory key comparison, a data analysis procedure for this comparison was proposed and recommended by CIPM [1, 2, 3], therein the degrees of equivalence of measurement standards of the laboratories participated in the comparison and the ones between each two laboratories were introduced but a corresponding clear and plausible measurement model was not given. Authors in [4] offered possible measurement models for a given comparison and a suitable model was selected out after rigorous analyzing steps for expectation values of these degrees of equivalence. The systematic laboratory-effects model was then selected as a right one in this report. Those models were all based on the one true value existence assumption. However in the year 2008, a new version of the Vocabulary for International Metrology (VIM) [7] was issued where the true value of a given measurement standard should be now perceived as multi true values which following a given statistics distribution. Applying this perception of true values of a measurement standard with combination of the steps in [4], measurement models have been developed and degrees of equivalence have been analyzed. The results show that although with new definition, the systematic laboratory-effects model is still the reasonable one in a given key comparison.