Dictionary · Uncertainty
Coverage factor
The number k by which a combined standard uncertainty is multiplied to obtain an expanded uncertainty; k = 2 is standard certificate practice, with a t-based k when effective degrees of freedom are small.
Related terms
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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
Type B evaluation of measurement uncertainty
Evaluation of a component of uncertainty by means other than statistical analysis of current measurements — calibration certificates, specifications, handbook data, assumed distributions.
VIM (JCGM 200:2012) 2.29
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꜀.
VIM (JCGM 200:2012) 2.31
Measurement uncertainty
A non-negative parameter characterizing the dispersion of the quantity values being attributed to a measurand, based on the information used — the quantitative expression of doubt about a result.
VIM (JCGM 200:2012) 2.26
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
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