Statistical remarks on laboratory-evaluating programs for comparing laboratories and methods

Abstract For third line quality control of laboratories participation in laboratory‐evaluating programs is recommended and sometimes obligated (accredited laboratories). The Wageningen Evaluating Programmes for Analytical Laboratories (WEPAL) currently organizes four such programs for agricultural and environmental laboratories. Within these programs, analytical data for many samples and elements/parameters from many laboratories are collected regularly, including information on methods of digestion/extraction (MIC1) and detection (MIC2). In this contribution the statistics used in these programs are explained.