Estimating Uncertainty: Methods & Definitions

METHODS

Different methods for estimating uncertainties:

- Intralaboratory : 

• Uncertainty Budget : applying the GUM (Guide to the expression of uncertainty in measurement)
• Uncertainty Budget : Monte-Carlo  
• Uncertainty Budget : Kragten

- Interlaboratory (intercomparisons) 

DEFINITIONS

Uncertainty: parameter, associated with the result of a measurement, that characterizes the dispersion of the values that could reasonably be attributed to the measurand.

Combined Uncertainty: standard uncertainty of the result of a measurement when that result is obtained from the values of a number of other quantities, equal to the positive square root of a sum of terms, the terms being the variances or covariances of these other quantities weighted according to how the measurement result varies with changes in these quantities.

Expanded Uncertainty: quantity defining an interval about the result of a measurement that may be expected to encompass a large fraction of the distribution of values that could reasonably be attributed to the measurand.

Coverage Factor: numerical factor used as a multiplier of the combined standard uncertainty in order to obtain an expanded uncertainty.

Repeatability: closeness of the agreement between the results of successive measurements of the same measurand carried out under the same conditions of measurement.

Reproducibility: closeness of the agreement between the results of measurements of the same measurand carried out under changed conditions of measurement.

Accuracy: closeness of the agreement between the result of a measurement and a true value of the measurand.

EMT: Maximum Permissible Error. Extreme value of the measurement error, with respect to a known reference quantity value, permitted by specifications or regulations for a given measurement, measuring instrument, or measuring system.

[Definitions from Guide to the expression of uncertainty in measurement  ]