CalculationMeasurement Uncertainty Budget
Measurement Uncertainty Budget
Combines independent components of a length measurement into standard and expanded uncertainty.
How to use the result
All contributions refer to the same measurand in millimetres with sensitivity coefficient one. Correlated quantities require an extended budget.
Correct known systematic deviations first. Do not include resolution or other contributions twice if they are already fully included in the calibration or repeatability contribution.
The factor k is specified. Degrees of freedom and distribution shape are not estimated; with small samples, k = 2 does not automatically provide 95 % coverage.
Formulas
uA = s / √n; uResolution = d / √12; uCal = UCal / kCal; uResidual = a / √3uc = √(uA² + uResolution² + uCal² + uResidual²)U = k × uc Sources: https://physics.nist.gov/cuu/Uncertainty/typea.html; https://physics.nist.gov/cuu/Uncertainty/typeb.html; https://physics.nist.gov/cuu/Uncertainty/combination.html; https://physics.nist.gov/cuu/Uncertainty/coverage.html