This paper proposes a measure for assessing the degree of equivalence between the two laboratories in a key comparison. The measure is called asymmetric degree of interchangeability. It is asymmetric since, based on this measure, a laboratory may be considered interchangeable with another laboratory but the converse may not be true. Fiducial procedures are presented for testing the hypothesis that a laboratory is (directionally) interchangeable with another. The procedure is based on comparing a probability measure, which is shown closely related to asymmetric degree of interchangeability, with an agreed upon threshold. Computer programs for calculating the p-value of the tests, written using open-source software, are listed.
equivalence, fiducial inference, test of hypotheses