TABLE OF CONTENTS John Hurll
The objective of a measurement is to determine the value of the measurand, that is, the specific quantity subject to measurement. A measurement begins with an appropriate specification of the measurand, the generic method of measurement and the specific detailed measurement procedure. Knowledge of the influence quantities involved for a given procedure is important so that the sources of uncertainty can be identified. Each of these sources of uncertainty will contribute to the uncertainty associated with the value assigned to the measurand.
The guidance in this chapter is based on information in the Guide to the Expression of Uncertainty in Measurement [1], hereinafter referred to as the GUM. The reader is also referred to the UKAS document M3003 Edition 2 [2], which uses terminology and methodology that are compatible with the GUM. M3003 is available as a free download at www.ukas.com.
A quantity ( Q) is a property of a phenomenon, body or substance to which a magnitude can be assigned. The purpose of a measurement is to assign a magnitude to the measurand: the quantity intended to be measured. The assigned magnitude is considered to be the best estimate of the value of the measurand.
The uncertainty evaluation process will encompass a number of influence quantities that affect the result obtained for the measurand. These influence, or input, quantities are referred to as X and the output quantity, that is, the measurand, is referred to as Y.
As there will usually...
