Statistical interpretation of key comparison degrees of equivalence based on distributions of belief

The Mutual Recognition Arrangement (MRA) requires the calculation of unilateral degrees of equivalence (DoE), defined as the difference between a laboratory's measurement and a key comparison reference value (KCRV). The functional form of the KCRV has been a source of much debate, with most of the proposed solutions being based on a frequentist interpretation of probability. The focus of this article is on the case when the result of each laboratory's measurement is interpreted as a mean and standard deviation of a probability distribution of belief about a measurand. Bayesian statistical methods are best suited to deal with this situation and lead to interesting insights about the form of the KCRV and the DoE.