7.7 Uncertainty estimation

The uncertainty of a measurement is a non-negative parameter characterizing the dispersion of the quantity values being attributed to a measurand, based on the information used. Uncertainty was defined until recently as the parameter associated with the result of a measurement, that characterises the dispersion of the values that could reasonably be attributed to the measurand.

Measurement uncertainty includes components arising from systematic effects, such as components associated with corrections and the assigned quantity values of measurement standards, as well as the definitional uncertainty. Sometimes estimated systematic effects are not corrected for but, instead, associated measurement uncertainty components are incorporated.

Measurement uncertainty comprises, in general, many components (uncertainty budget). Some of these contributions to the combined uncertainty may be evaluated by Type A evaluation by relying on the statistical distribution of the quantity values arising from series of replicate measurements and can be characterized by its standard deviations. The other components, which may be evaluated by Type B evaluation of measurement uncertainty, can also be characterized by standard deviations, evaluated from probability density functions based on experience or from other sources of information (such as the method theoretical model).

Reference: Eurachem/CITAC guide CG4: Quantifying Uncertainty in Analytical Measurement. Third edition 2012.