GUM is short for the Guide to the Expression of Uncertainty in Measurement, the internationally adopted document that sets out the standard approach: build a measurement model, evaluate standard uncertainties by Type A or Type B methods, combine them with the law of propagation and expand with a coverage factor. Supplements extend it to Monte Carlo propagation and multiple outputs. Accredited calibration labs are expected to evaluate uncertainty in line with it.
That's not a GUM-compliant budget, you added the expanded uncertainties straight up instead of combining standard uncertainties.
Labs say 'GUM method' for the classic propagation route, as opposed to 'Monte Carlo' for the supplement method.
Also heard as
- the Guide
- JCGM 100
Related terms
Law of propagation of uncertainty
The first-order formula that combines input standard uncertainties, weighted by sensitivity coefficients, into the output uncertainty.
Type A evaluation
Putting a number on an uncertainty component by running statistics on your own repeat readings.
Type B evaluation
Sizing an uncertainty component from existing knowledge such as certificates, specs or resolution, with no new repeat data.
Monte Carlo method
Propagating uncertainty by random sampling of input distributions through the measurement model, many thousands of times.
Standard uncertainty
Uncertainty expressed as one standard deviation, the common currency for combining uncertainty components.