Expression of Uncertainty in Measurement

ISO (1993) Guide to the expression of uncertainty in measurement. ISBN 92-67-10188-9, ist Edn., Geneva, Switzerland. 

The proper application of the ISO Guide to the expression of uncertainty in measurement requires that aU sources of rmcertainty are included. In practical terms this means an uncertainty budget has to be developed also by the user. The development of an rmcertainty budget, and the consequences for both analysts and producers is described later in Section 7.2. 

Pauwels (1999) argues that the certified values of CRMs should be presented in the form of an expanded combined uncertainty according to the ISO Guide on the expression of uncertainty in measurement, so that coverage factor should always be clearly mentioned in order to allow an easy recalculation of the combined standard uncertainty. This is needed for uncertainty propagation when the CRM is used for calibration and the ISO Guide should be revised accordingly. The use of the expanded uncertainty has been pohcy in certification by NIST since 1993 (Taylor and Kuyatt 1994). 

ANSI and NCSL, U.S. Guide to the Expression of Uncertainty in Measurement, 1800 30 Str., Suite 305B, Boulder, CO 80301, USA, ANSI/NCSLZ540-2-1997, (1997). 

The Guide to the Expression of Uncertainty in Measurement (GUM) to some extent is the Bible of uncertainty estimation. Since it was originally made for physical measurements in metrology laboratories, it is quite difficult to translate it into analytical chemistry problems, especially for routine measurements. 

The approach to measurement uncertainty that is espoused by many authorities, including the VIM, is embodied in a standard called the Guide to the Expression of Uncertainty in Measurement, universally referred to as... 

ISO (1995) Guide Expression of Uncertainty in Measurement, Leitfaden zur Angabe der Unsicherheit beim Messen (GUM), Joint publication with BIPM, IEC, IFCC,... 

The definition of metrological traceability (see above) stipulates that each link in the chain has a known uncertainty. Nowadays, this concept and its application have been reformulated by the BIPM and recently detailed in the Guide to the expression of uncertainty in measurement (GUM) [26] parameter, associated with the result of a measurement, that characterizes the dispersion of the values that could reasonably be attributed to the measurand . Useful explanations are provided in several other guides [26-30] as well as commentaries [e.g. 31-33], The philosophy is to apply a bot-tom-up approach by formulating a function of all input quantities giving the measurand as output. An uncertainty budget of all sources of uncertainty is established. Important items to consider are ... 

In the IMEP programme1, Si-traceable values with a full measurement uncertainty according to the Guide to the expression of uncertainty in measurement (GUM) are disseminated by IRMM to field (and other) laboratories by means of appropriately prepared test samples. The uncertainties are the end-product of an evaluation process of all uncertainty sources which is as complete as... 

The expanded uncertainty U is obtained by multiplying crx by an appropriate coverage factor (k) as specified in the Guide to the expression of Uncertainty in Measurements (GUM). Thus U=kax and X. U. 

Guide to the Expression of Uncertainty in Measurement, ISBN 92-67-10188-9, International Organization for Standardization, Geneve 1993, orders at http //www.iso.ch/infoe/other-pub.html Metrology and measurement... 

International Organization for Standardization, Guide to the Expression of Uncertainty in Measurement, Geneva, 1995. 

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