Dictionary · Uncertainty
Standard measurement uncertainty
Measurement uncertainty expressed as a standard deviation, denoted u — the common currency into which all components are converted before combination.
Related terms
More from Uncertainty
Type A evaluation of measurement uncertainty
Evaluation of a component of uncertainty by statistical analysis of measured values obtained under defined conditions — e.g. the standard deviation of the mean of repeated readings.
VIM (JCGM 200:2012) 2.28
Welch–Satterthwaite formula
The formula for estimating the effective degrees of freedom of a combined standard uncertainty from the degrees of freedom of its components — used to select a coverage factor from the t-distribution.
GUM (JCGM 100:2008) G.4
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
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.
VIM (JCGM 200:2012) 2.35
Definitional uncertainty
The component of uncertainty resulting from the finite detail in the definition of the measurand itself — the floor below which no better procedure can go without redefining the quantity.
VIM (JCGM 200:2012) 2.27
Measurement model
The mathematical relation among all quantities known to be involved in a measurement, of the general form f(Y, X₁, …, Xₙ) = 0.
VIM (JCGM 200:2012) 2.48