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, and 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)    a discussion of the implications of the definitions of intermediate precision measures; b)    a guidance on the interpretation and application of the estimates of intermediate precision measures in practical situations; c)    determining reproducibility, repeatability and selected measures of intermediate precision; d)    improved determination of reproducibility and other measures of precision; e)    improving the estimate of the sample mean; f)     determining the range of in-house repeatability standard deviations; g)    determining other precision components such as operator variability; h)    determining the level of reliability of precision estimates; i)     reducing the minimum number of participating laboratories by optimizing the reliability of precision estimates; j)     avoiding distorted estimations of repeatability (split-level designs); k)    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.