KAN-G-01 Issue Number : 4
07 April 2016
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3. GENERAL CONCEPTS
The objective of a measurement is to determine the value of the measurand that involve specification of the measurand, the method of measurement and the procedure
of measurement. In general, the result of a measurement is only an estimate or approximation of the
value of the measurand, therefore the result is complete only when accompanied by the statement of the uncertainty of the estimate.
Uncertainty is a measure of the dispersion that may reasonably be associated with the measured value. It gives a range, centered on the measured value, within which, to a
stated probability, the true value lies. The uncertainty of the result of a measurement reflects the lack of exact knowledge of
the value of the measurand. The result of a measurement after correction for recognized systematic effects is still only an estimate of the value of the measurand
because of the uncertainty arising from random effects and from imperfect correction of the systematic effects.
The concept of uncertainty is based on the observable quantities obtained by measurement; this differs from the ideal concept of error based on the unknowable
quantities. Traditionally, an error of a measurement result is considered as having two components, namely random component and systematic component. Random error
presumably arises from unpredictable or stochastic temporal and spatial variations of influence quantities. Systematic error arises from a recognized effect of an influence
quantity of a measurement result. The difference between error and uncertainty should always be borne in mind. For
example, the result of a measurement after correction can unknowably be very close to the unknown value of the measurand, and thus have negligible error, even though it
may have a large uncertainty.
KAN-G-01 Issue Number : 4
07 April 2016
9 Dokumen ini tidak dikendalikan jika diunduh Uncontrolled when downloaded
4. SOURCES OF UNCERTAINTY
