Meteorological Instrument Performance Characteristics

General Characteristics of Measurements » Uncertainty » Evaluating Uncertainty

Type A evaluation of standard uncertainty may be based on any valid statistical method for analyzing data. The analysis of variance (ANOVA) is particularly useful since it considers both random and systematic effects between groups relative to the random effects within groups.

In Type B evaluation cases, a target is to have the uncertainty correspond to similar coverage. Type-B estimates are difficult to defend as quantitative measures and can't be assigned rigorous confidence limits.

A Type B evaluation of standard uncertainty is usually based on scientific judgment using all the relevant information available about the measurand and the instrument, such as:

  • Previous measurement data
  • Experience with the properties and behavior of instruments
  • Manufacturer’s specifications
  • Calibration data
  • Uncertainties associated with reference data
    • Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results (Taylor and Kuyatt, 1994)
Type B evaluation of standard uncertainty.

The combined standard uncertainty of a measurement result uC is obtained by combining the individual standard uncertainties whether arising from Type A or Type B evaluations.


Select the type of uncertainty (Type A or Type B) referred to by the statement.

a) Affected by previous measurement data or reference data uncertainties:
Please make a selection.
b) Uncertainty in calibration:
Please make a selection.
c) Evaluation based on statistical methods:
Please make a selection.
d) Evaluation based on scientific judgement using relevant information:
Please make a selection.

The correct answers are shown above.

Please make a selection.