ABSTRACT
Physical measurement is a fundamental activity of everyday life and an essential component of science and medicine. In medicine, measurement plays a vital role in patient management. This chapter introduces the concepts of precision and accuracy as needed in instrument evaluation. Another crucial step in instrument validation is to check if the device is conforming with its clinical expectation and also if practical guideline is provided for immediate clinical use. Precision errors reflect the reproducibility of the technique. They measure the ability of a method to measure a parameter consistently over multiple measurements, so a precise measurement has nearly the same value each time it is measured. Precision errors can be further separated into short-term and long-term. Short-term precision errors characterize the reproducibility of a technique and in bone densitometry are useful in describing the limitations of measuring changes in skeletal status.
