Dictionary · Uncertainty
Target measurement uncertainty
An uncertainty specified in advance as an upper limit, decided from the intended use of the result.
Related terms
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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
Rectangular distribution
A probability distribution assigning equal likelihood everywhere between limits ±a. Used for Type B components where only limits are known; its standard uncertainty is a/√3.
GUM (JCGM 100:2008) 4.3.7
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
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
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
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