CHAPTER 8 – Calibration and Accuracy

Calibration and metrology is an immense topic with numerous aspects. Calibration is particularly vital with respect to synthetic instruments. In the science of metrology, the measurand is the thing one is trying to measure. The central point is that a measurand is specified in the context of a measurement method. The word accuracy as used in common technical discussion is often used inaccurately from a metrology perspective. According to CIPM, NIST, and other metrology standard setters, accuracy is the “closeness of the agreement between the result of a measurement and the value of the measurand.” This is a qualitative concept. Accuracy has nothing to do with numbers. In addition, the word precision , also a qualitative concept, is defined by ISO 3534-1 as “the closeness of agreement between independent test results obtained under stipulated conditions.” Both precision and accuracy are qualitative terms. Therefore, to talk quantitatively about the qualitative term accuracy, or, for that matter precision, repeatability, reproducibility, variability, and uncertainty, one needs to use statistical theory.