5. Principles of measurement uncertainty estimation

Brief summary: The main principles of measurement uncertainty estimation – the so-called GUM principles – are presented on the example of determination of pesticides in oranges. These principles have been laid down in the ISO GUM [1]ISO GUM originally refers to the Guide To The Expression of Uncertainty in Measurement, ISO, Geneva, Switzerland, 1993 (Reprinted 1995). In 2008 this document was revised and reissued as ISO JCGM 100:2008 Evaluation of measurement data - Guide to the expression of uncertainty in measurement. The latter document is available on-line from http://www.bipm.org/en/publications/guides/gum.html  and they are now universally accepted as being the common foundation of all the different uncertainty estimation approaches. These principles are the following:

1. The basis of any measurement (thus obviously also measurement uncertainty evaluation) is the definition of the measurand;
2. The used measurement procedure has to correspond to the measurand definition;
3. All relevant sources of uncertainty have to be carefully considered and those that are important have to be taken into account;
4. The random and systematic effects are treated the same way when estimating measurement uncertainty – both are evaluated as standard uncertainties, which thereafter are combined into the combined standard uncertainty.