Dictionary · Uncertainty
Combined standard measurement uncertainty
The standard uncertainty obtained from the individual standard uncertainties (and covariances) of the input quantities through the measurement model — root-sum-of-squares in the uncorrelated case, denoted u꜀.
Related terms
More from Uncertainty
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
Coverage interval
The interval containing the set of true quantity values of a measurand with a stated probability, based on available information — unlike a classical confidence interval, not necessarily centred on the measured value.
VIM (JCGM 200:2012) 2.36
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
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
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
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