Dictionary · Uncertainty
Expanded measurement uncertainty
The product of a combined standard uncertainty and a coverage factor greater than one: U = k·u꜀. With k = 2 the coverage probability is about 95 % for a normal distribution.
Related terms
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Triangular distribution
A probability distribution rising linearly to a peak midway between limits ±a. Used when values near the centre are more likely; its standard uncertainty is a/√6.
GUM (JCGM 100:2008) 4.3.9
Input quantity in a measurement model
A quantity that must be measured, or whose value can be otherwise obtained, to calculate a measured value of the measurand.
VIM (JCGM 200:2012) 2.50
Relative standard measurement uncertainty
A standard uncertainty divided by the absolute value of the measured quantity value — the form specifications and CMCs often quote (parts in 10⁶, percent of reading).
VIM (JCGM 200:2012) 2.32
Coverage probability
The probability that the set of true quantity values of a measurand is contained within a specified coverage interval — commonly 95 % in calibration practice.
VIM (JCGM 200:2012) 2.37
Uncertainty budget
A statement of a measurement uncertainty, its components, and their calculation and combination — usually tabulated with each source, evaluation type, distribution, standard uncertainty, sensitivity coefficient, and contribution.
VIM (JCGM 200:2012) 2.33
Monte Carlo method (uncertainty)
Propagation of probability distributions through a measurement model by repeated random sampling, per JCGM 101:2008. Preferred when the model is strongly non-linear or distributions are non-normal.
JCGM 101:2008