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Critical Assessment of Current Practice in the Analysis of Key Comparison Data with Suggested Improvements

Published

Author(s)

Blaza Toman, Clemens Elster

Abstract

The current practice in the analysis of key comparison data is discussed and critically assessed. We argue that there is an ambiguity in the definition and meaning of the (unilateral) degrees of equivalence as defined in the MRA. This ambiguity can be avoided by specifying the quantities that are to be estimated by the degrees of equivalence, and we propose a standard statistical model to do this. We then show that the degrees of equivalence are not a unique measure of consistency between the results and the underlying measurand when determined solely from the data. Prior knowledge or additional assumptions are needed for this purpose, and Bayesian methods are particularly suitable to handle that. However, such measures of equivalence depend on the chosen additional assumptions and generally are not in accordance with the current MRA. Fortunately, quantifying consistency between the results and the underlying measurand is not necessary in order to assess equivalence between the laboratories. We show that on the basis of the (unambiguous) pairwise degrees of equivalence the laboratories can be grouped into equivalent subsets, the largest of which may be chosen to select those laboratories whose CMCs are then viewed as validated.
Citation
Metrologia
Volume
50

Keywords

Key Comparison experiments, unilateral degrees of equivalence, Mutual Recognition Agreement, Calibration and Measurement Capability.

Citation

Toman, B. and Elster, C. (2013), Critical Assessment of Current Practice in the Analysis of Key Comparison Data with Suggested Improvements, Metrologia (Accessed April 20, 2024)
Created October 3, 2013, Updated January 27, 2020