Statistical aspects of the planning and analysis of collaborative studies on biological standards

Statistical principles play a central role in the planning and analysis of collaborative studies on biological standards. These studies are carried out to assess the suitability of proposed biological standards, which should be demonstrated to provide valid and reproducible measurements of biological potency, and to assign units of activity (for example, by calibration against an existing standard). Guidelines have been published by the World Health Organization (WHO Tech Rep Ser 1978: 626: 101-141) describing the technical and general aspects of setting up biological standards and organizing collaborative studies. This paper, which is complementary to the WHO guidelines, expands on the statistical points which need to be considered. The general design of the study, the design of individual assays, the statistical analysis of the raw data, and the presentation of the results are described.