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Accuracy ○｜Definition｜1st｜20260130121224-00-⌔
Accuracy and precision - Wikipedia
Accuracy and precision
Accuracy and precision are measures of observational error; accuracy is how close a given set of measurements is to the true value and precision is how close the measurements are to each other.
The International Organization for Standardization (ISO) defines a related measure:1 trueness, “the closeness of agreement between the arithmetic mean of a large number of test results and the true or accepted reference value.”
While precision is a description of random errors (a measure of statistical variability), accuracy has two different definitions:
- More commonly, a description of systematic errors (a measure of statistical bias of a given measure of central tendency, such as the mean). In this definition of “accuracy”, the concept is independent of “precision”, so a particular set of data can be said to be accurate, precise, both, or neither. This concept corresponds to ISO’s trueness.
- A combination of both precision and trueness, accounting for the two types of observational error (random and systematic), so that high accuracy requires both high precision and high trueness. This usage corresponds to ISO’s definition of accuracy (trueness and precision).2
Printed 2026-06-28.
Link to original Footnotes
BS ISO 5725-1: “Accuracy (trueness and precision) of measurement methods and results - Part 1: General principles and definitions.”, p.1 (1994) ↩
Menditto, Antonio; Patriarca, Marina; Magnusson, Bertil (2007-01-09). “Understanding the meaning of accuracy, trueness and precision”. Accreditation and Quality Assurance. 12 (1): 45–47. doi:10.1007/s00769-006-0191-z. ISSN 0949-1775. ↩
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