A structured breakdown of a measurement's uncertainty: each row names a source and gives its estimate, assumed distribution, divisor, standard uncertainty, sensitivity coefficient, contribution in output units and degrees of freedom. The rows are combined into the combined and expanded uncertainty at the bottom. Assessors read budgets line by line, and the ranked contributions show where money spent on better equipment or tighter conditions would actually pay off.
Pull up the uncertainty budget for the 1 kV range, the divider ratio is eating 70 percent of it.
Rank the contributions by size before arguing about any of them; usually two or three lines decide everything and the rest is rounding.
Also heard as
- budget
- uncertainty analysis
- error budget
Related terms
Combined standard uncertainty
The total standard uncertainty of a result, found by combining all input uncertainties through the measurement model.
Sensitivity coefficient
The factor that converts an input's uncertainty into its effect on the output, the partial derivative of the model.
Imported uncertainty
The uncertainty carried into a measurement from the calibration certificate of the reference standard used.
Double counting
Budget slang for entering the same physical effect twice under different names, which inflates the uncertainty.
Type B evaluation
Sizing an uncertainty component from existing knowledge such as certificates, specs or resolution, with no new repeat data.