POOLED DATA DISTRIBUTIONS: GRAPHICAL AND STATISTICAL TOOLS FOR EXAMINING COMPARISON REFERENCE VALUES

Measurement comparison data sets are generally summarized using a simple statistical reference value calculated from the pool of the participants’ results. This reference value can become the standard against which the performance of the participating laboratories is judged. Consideration of the comparison data sets, particularly with regard to the consequences and implications of such data pooling, can allow informed decisions regarding the appropriateness of choosing a simple statistical reference value. Recent key comparison results drawn from the BIPM database are examined to illustrate the nature of the problem, and the utility of a simple approach to creating pooled data distributions. We show how to use detailed analysis when arguing in favor of a KCRV, or when deciding that a KCRV is not always warranted for the particular data sets obtained experimentally.