This standard has been derived from the International Organization for Standardization (ISO) U.S. Guide to the Expression of Uncertainty in Measurement to promote consistent international Methods in the expression of measurement uncertainty within U.S. standardization, calibration, laboratory accreditation, and metrology services. It is identical to the ISO Guide (corrected and reprinted, 1995) with the exception of minor editorial changes to facilitate it's use in the United States. These changes are as follows: (1) a dot on the line is used as the decimal marker instead of a comma, (2) the spelling of words is in accordance with Webster's Third New International Dictionary instead of the Oxford English Dictionary, and (3) the running heads on pages are partially modified.