Reliability of repeatability and reproducibility measures in collaborative trials.

The acceptability of a new analytical method is generally assessed in terms of repeatability and reproducibility estimates derived from a collaborative study. Procedures are presented for calculating confidence intervals and operating characteristic curves for acceptance criteria based on the repeatability and reproducibility estimates. Comparisons of the reliability of estimates are provided for various numbers of collaborators. With a small number of collaborators, the estimates of reproducibility are not reliable and decisions regarding acceptability of a method will be heavily based on the method's repeatability rather than the property of most interest, namely, the reproducibility of the method.