A Type B standard uncertainty is determined from a probability distribution specified by scientific judgment based on all available information. The ISO-GUM discusses symmetric distributions only. Sometimes an asymmetric distribution is needed. We describe a trapezoidal distribution that may be asymmetric. Triangular and rectangular distributions are special cases of trapezoidal distribution. Then we discuss how a trapezoidal distribution may be used to determine an asymmetric correction for bias and its associated standard uncertainty.
Pub Type: Journals
ISO-GUM, measurement uncertainty, rectangular distribution uncertainty, variance components