The generally accepted approach to evaluating and expressing uncertainties in measurements
undertaken by testing and calibration laboratories is given in The Guide to the expression of
Uncertainty in Measurement, first published in 1993 by ISO, Geneva. That document, frequently
referred to as The Guide or the GUM, presents a comprehensive study of these principles which, if
followed, will ensure that measurement uncertainty is calculated and stated in a consistent manner in all
situations. It is, however, a complex document and it has been found necessary to supplement it with
simplified guidance for specific fields of measurement.
05 Apr 2006