Significance and Use 5.1 This guide is intended to help testing laboratories and the developers of methods and software for those laboratories to apply the concepts of measurement uncertainty to radiochemical analyses. 5.2 The result of a laboratory measurement never exactly equals the true value of the measurand. The difference between the two is called the error of the measurement. An estimate of the possible magnitude of this error is called the uncertainty of the measurement. While the error is primarily a theoretical concept, since its value is never known, the uncertainty has practical uses. Together, the measured value and its uncertainty allow one to place bounds on the likely true value of the measurand. 5.3 Reliable measurement-based decision making requires not only measured values but also an indication of their uncertainty. Traditionally, significant figures have been used with varying degrees of success to indicate implicitly the order of magnitude of measurement uncertainties; however, reporting an explicit uncertainty estimate with each result is more reliable and informative, and is considered an industry-standard best practice.Scope 1.1 This guide provides concepts, terminology, symbols, and recommendations for the evaluation and expression of the uncertainty of radiochemical measurements of water and other environmental media by testing laboratories. It applies to measurements of radionuclide activities, including gross activities, regardless of whether they involve chemical preparation of the samples. 1.2 This guide does not provide a complete tutorial on measurement uncertainty. Interested readers should refer to the documents listed in Section 2 and References for more information. See, for example, GUM, QUAM, Taylor and Kuyatt (1)2, and Chapter 19 of MARLAP (2). 1.3 The system of units for this guide is not specified. Dimensional quantities in the guide are presented only as illustrations of calculation methods. The examples are not binding on products or test methods treated. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
