International Standardization Organization uncertainty

Measurement uncertainty is defined by the International Standards Organization (ISO) as a parameter associated with the result of a measurement that characterizes the dispersion of the values that could reasonably be attributed to the measurand. The uncertainty is expressed as a range within which the tme value of the measurand is believed to lie. In a practical sense, measurement uncertainty can be considered as a measure of the quality of measurement results. It gives an answer to the question How well does the result represent the value of the quantity being measured Therefore, the measurement uncertainty associated with a result is an essential part of quantitative results, and along with traceability, it can allow users to assess the reliability of the result and compare results among different sources or with reference values. 

International Standards Organization, ISO Guide 98-3, Uncertainty of Measurement—Part 3 Guide to the Expression of Uncertainty in Measurement (GUM 1995), Geneva, 2008. 

International Standards Organization, ISO 21748, Guidance for the Use of Repeatability, Reproducibility and Trueness Estimates in Measurement Uncertainty Estimation, Geneva, 2004. 

It is a requirement imder ISO/IEC 17025 that laboratories determine and provide evidence on the imcertainty associated with analytical results. Measurement imcertainty is a quantitative indicator of the confidence in the analytical data. It describes the range around an experimental result within which the true value can be expected to lie with a defined probability (confidence level). Uncertainty can be estimated using an International Standards Organization (ISO) [38] or Eur-achem approach [39]. 

International Standards Organization (1995) Guide to expression of Uncertainty in Measurement, ISO, Geneva. 

The first round of key comparisons in these fields was largely completed by the end of 1999 and showed that gas analysis, elemental analysis and pH measurement are already rather well developed and mature areas, whereas organic analysis, for example in the clinical and food areas, requires more attention, in particular with respect to sampling and sample pretreatment which are often the major sources of uncertainty. As regards sampling which is even more important when field measurements are linked up with national or international standards, comprehensive practical and theoretical knowledge is available, especially for particulate material sampling [7], which can be used where applicable to improve the comparability of chemical measurement results. 

Ingamells CO, PiTARD FF (1986) Applied Geochemical Analysis, pp L-84.Wiley, New York. International Federation of Clinical Chemistry (IFCC) (1978) Expert Panel on Nomenclature and Principles of Quality Control in Clinical Chemistry. Clin Chim Acta 83 L89F-202F. International Organization for Standardization (ISO) (1993) Guide to the expression of uncertainty. Geneva. 

ISO (1993) International Organization for Standardization, Guide to the expression of uncertainty in measurement. Geneva... 

Results from all participants according to uncertainties calculated within the Guidelines of Quantifying Measurement Uncertainty issued by the International Organization for Standardization (ISO,1995) and/or EURACHEM/CITAC (2000). 

Guide to the expression of uncertainty. ISO/IEC/OIML/BIPM, 1992, ISO, Geneve,CH. Certification of Reference Materials - Genera and Statistical Principles. ISO Guide 35, International Organization for Standardization, Geneva, Switzerland (1985). 

ISO, Guide to the Expression of Uncertainty in Measurement, International Organization for Standardization, Geneva, Switzerland, 1993. Several supplements have been published see Bich, W., Cox, M. C., and Harris, P. M., Evolution of the Guide to the Expression of Uncertainty in Measurement," Metrologia 43, S161,2006. 

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