scope:

This document provides a) a discussion of alternative experimental designs for the determination of trueness and precision measures including reproducibility, repeatability and selected measures of intermediate precision of a standard measurement method, including a review of the circumstances in which their use is necessary or beneficial, and guidance as to the interpretation and application of the resulting estimates; b) worked examples including specific designs and computations. Each of the alternative designs discussed in this document is intended to address one (or several) of the following issues: a) determining reproducibility, repeatability and selected measures of intermediate precision; b) improved1 determination of reproducibility and other measures of precision; c) improving the estimate of the sample mean; d) determining the range of in-house repeatability standard deviations; e) determining other precision components such as operator variability; f) determining the level of reliability of precision estimates; g) reducing the minimum number of participating laboratories by optimizing the reliability of precision estimates; h) avoiding distorted estimations of repeatability (split-level designs); i) avoiding distorted estimations of reproducibility (taking the heterogeneity of the material into consideration). Often, the performance of the method whose precision is being evaluated in a collaborative study will have previously been assessed in a single-laboratory validation study conducted by the laboratory which developed it. Relevant factors for the determination of intermediary precision will have been identified in this prior single-laboratory study.