Some Important Definitions

Abstract

The very nature of all physical measurements suggests that it is impossible to carry out a measurement of any physical quantity with no error. Hence, whenever the value of a physical quantity is determined through a measurement process, it is only the best estimate of the value of the physical quantity obtained from the given experimental data. The estimated value may be slightly less or more than the true value of the physical quantity. In an experimental work, basically four major elements are involved, namely (1) instruments, (2) observer, (3) measurement process, and (4) statistics. The instruments include environment conditions and influence quantities. Even when appropriate corrections for known or suspected sources of errors have been applied, there still remains an uncertainty, that is, a doubt about how well the result of a measurement represents the true value of the quantity being measured. During a measurement, the errors may creep in due to inherent error in instruments, effect of environment on an instrument reading, the error in reading the instrument by the observer and errors incurred due to a particular process of measurement. So when giving a measured value of any quantity, one will never be sure enough to give a specific value but would like to say that measured value of the same quantity may lie in a certain range.