A method of evaluating a standard uncertainty from available knowledge rather than a new statistical sample: calibration certificates, manufacturer specifications, resolution, handbook values, earlier data and engineering judgment. The analyst assigns a probability distribution to the information and converts it to a standard deviation, for example dividing a ±0.5 °C spec limit by the square root of 3 for a rectangular distribution. Once expressed as standard uncertainties, Type B components carry the same weight as Type A.
Type B for the reference is straight off its cert, 1.2 ppm at k equals 2, so 0.6 ppm standard.
Also heard as
- Type B
- Type B uncertainty
Related terms
Type A evaluation
Putting a number on an uncertainty component by running statistics on your own repeat readings.
Rectangular distribution
A distribution giving equal likelihood to every value between two limits, used when only the bounds are known.
Imported uncertainty
The uncertainty carried into a measurement from the calibration certificate of the reference standard used.
Standard uncertainty
Uncertainty expressed as one standard deviation, the common currency for combining uncertainty components.
Spec
Shop clipping for a manufacturer's accuracy specification, the published limits an instrument should stay within.