Rules for stating when a limiting value is exceeded

Abstract

The paper describes rules for stating whether a measurement result indicates that the value of the measurand, e.g. the concentration of a substance in the blood, is in conformity or not in conformity with given specifications. Examples of the intended applications are control of doping in sports, alcohol level in drivers’ blood, trace metals levels in workers’ blood, the proportion of gold in alloys, certain ingredients in food products and pesticides in drinking water. When limiting value(s) have been established a permissible measurand value is said to be in conformity and a non-permissible value it is said to be in non-conformity. One of the following three statements is asserted: Statement A: The value of the measurand is beyond any reasonable doubt in conformity, Statement B: The value of the measurand is beyond any reasonable doubt in non-conformity, Statement C: Neither conformity nor non-conformity could be demonstrated. The test can be performed as either a one-stage or a two-stage procedure. A two-stage procedure is recommended as especially appropriate when a cheap and fast screening method can be used in the first stage. For normally distributed measurements, a freeware computer program, conform1e.exe, is available for the calculations of the probabilities for Statements A, B and C.