The problem of determining a consensus value and its uncertainty from the results of multiple methods or laboratories is discussed. Desirable criteria of a solution are presented. A solution motivated by the ISO Guide to the Expression of Uncertainty in Measurement (ISO GUM) is introduced and applied in a detailed worked example. A Bayesian hierarchical model motivated by the proposed solution is presented and compared to the solution.

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A statistical analysis for key comparisons with linear trends is proposed. The approach has the advantage that it is consistent with the no-trend cases. The uncertainties for the key comparison reference value, which is time dependent in this case, and the degrees of equivalence are also provided. As an example, the approach is applied to key comparison CCEM-K2.

A statistical analysis for key comparisons with linear trends and multiple artefacts is proposed. This is an extension of a previous paper for a single artefact. The approach has the advantage that it is consistent with the no-trend case. The uncertainties for the key comparison reference value and the degrees of equivalence are also provided. As an example, the approach is applied to key comparison CCEM–K2.

A generalized statistical approach for interlaboratory comparisons with linear trends is proposed. This new approach can be applied to the general case when the artefacts are measured and reported multiple times in each participating laboratory. The advantages of this approach are that it is consistent with the previous approaches when only the pilot lababoratory makes multiple measurements and it applies whether or not there exists a trend. The uncertainties for the comparison reference value and the degree of equivalence are also provided. As an illustration, the method is applied to the SIM.EM-K2 comparison for resistance at the level of 1 G .