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
Measurement function
The function whose output value, computed from the input quantity values, is the measured value of the output quantity — Y = f(X₁, …, Xₙ) when the model can be solved explicitly.
VIM (JCGM 200:2012) 2.49
Standard measurement uncertainty
Measurement uncertainty expressed as a standard deviation, denoted u — the common currency into which all components are converted before combination.
VIM (JCGM 200:2012) 2.30
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
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 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
Sensitivity coefficient
The partial derivative ∂f/∂xᵢ of the measurement model with respect to an input quantity, evaluated at the estimates: it converts an input standard uncertainty into its contribution to the uncertainty of the result.
GUM (JCGM 100:2008) 5.1.3