Definitions of Terms Related to Accuracy Precision is the ability to produce the same value within given accuracy bounds when successive readings of a specific quantity are measured.
Precision represents the maximum departure of all readings from the mean value of the readings.
Thus, a measurement cannot be more accurate than the inherent precision of the combined primary and secondary precision. Error is the deviation of a measurement, observation, or calculation from the truth. The deviation can be small and inherent in the structure and functioning of the system and be within the bounds or limits specified. Lack of care and mistakes during fabrication, installation, and use can often cause large errors well outside expected performance bounds. Since the true value is seldom known, some investigators prefer to use the term Uncertainty .