Terminology

Is there a difference between accuracy, resolution, repeatability, and precision? Please read the following important definitions in the calibration world:

The degree of agreement of a measured value with the true or expected value of the quantity of interest. [NIST SP 260-100 Handbook for SRM Users]

A quantitative expression of the ability of an indicating device to distinguish meaningfully between closely adjacent values of the quantity indicated. [NCSL RP-2]

The closeness of the agreement between the results of a sample of measurements of a given measurand carried out using the same measurement procedure, using the same measuring and test equipment, under the same conditions of use and environment.

These conditions include:

• Reduction to a minimum of the variations due to the observer
• The same measurement procedure
• The same observer
• The same measuring equipment, used under the same conditions
• The same location
• Repetition over a short period of time.

The degree of mutual agreement characteristic of independent measurements as the result of repeated application of the process under specified conditions. Precision is concerned with the closeness together of results. [NIST SP 260-100 Handbook for SRM Users]

Comparison of a measurement standard or instrument with another standard or instrument to report or eliminate, by adjustment, any variation or deviation in the accuracy of the item being compared. [NIST SP 260-100 Handbook for SRM Users]

To perform the measurement process and act of evaluating, determining, and reporting the performance of measuring and test equipment (MTE), measurement/test systems (M/TS), or measurement standards (MS) to specified performance tolerance requirements through comparison to measurement standards systems of known and higher accuracy. [NCSL RP-3]

The range of values within which the true value is estimated to lie. It is a best estimate of possible inaccuracy due to both random and systematic errors. [NIST SP 260-100 Handbook for SRM Users]