Removing divergence of JCGM documents from the GUM (1993)
Raghu N. Kacker
The stated mission of the Joint Committee for Guides in Metrology (JCGM) is to maintain and promote the use of the Guide to the Expression of Uncertainty in Measurement (GUM) and the International Vocabulary of Metrology (VIM, 2nd edition). The JCGM has produced the third edition of the VIM (referred to as VIM3) and a number of documents referred to as supplements to the GUM. The signal contribution of the GUM is its operational view of the uncertainty in measurement as a parameter that characterizes the dispersion of the values that could be attributed to an unknown quantity. The operational view disconnected uncertainty from the unknowable quantities true value and error. The JCGM supplements effectively abandoned the operational view of the uncertainty and restored a pre-GUM idea of uncertainty and called it coverage interval, which is defined as an interval containing the true value of a quantity with a stated probability. The JCGM idea of coverage interval reconnected uncertainty with true value via (degree of belief) probabilities. The disparities of the JCGM documents from the GUM are undermining the signal contribution of the GUM, its operational view of the uncertainty in measurement. Either these disparities should to be removed or the JCGM documents should not be referred to as supplements to the GUM.