The closeness of the agreement between the result of a measurement and the true value of the measurand. [ ISO/IEC 14143-3, ISO/IEC/IEEE 24765 ]
- Accuracy is a qualitative concept. The term precision should not be used for "accuracy"[]. A true value is a value consistent with the definition of a given particular quantity and this is a value that would be obtained by a perfect measurement. In contexts where perfect measurement is not practically feasible, a conventional true value is a value attributed to a particular quantity and accepted, sometimes by convention, as having an uncertainty appropriate for a given purpose. 'Conventional true value', in the same reference, is sometimes called assigned value, best estimate of the value, conventional value or reference value. The accuracy should be expressed in terms of the Mean magnitude of relative error. [ ISO/IEC 14143-3 ]
