Editing Accuracy and precision (section)

==Common technical definition==
In simpler terms, given a [[statistical sample]] or set of data points from repeated measurements of the same quantity, the sample or set can be said to be ''accurate'' if their [[average]] is close to the true value of the quantity being measured, while the set can be said to be ''precise'' if their [[standard deviation]] is relatively small.

In the fields of [[science]] and [[engineering]], the accuracy of a [[measurement]] system is the degree of closeness of measurements of a [[quantity]] to that quantity's true [[value (mathematics)|value]].<ref name=metrology_terms>[http://www.bipm.org/utils/common/documents/jcgm/JCGM_200_2008.pdf JCGM 200:2008 International vocabulary of metrology] — Basic and general concepts and associated terms (VIM)</ref> The precision of a measurement system, related to [[reproducibility]] and [[repeatability]], is the degree to which repeated measurements under unchanged conditions show the same [[result]]s.<ref name=metrology_terms /><ref name=Taylor>{{cite book  |title=An Introduction to Error Analysis: The Study of Uncertainties in Physical Measurements |first= John Robert |last= Taylor |url=https://books.google.com/books?id=giFQcZub80oC&pg=PA128 |pages=128–129 |isbn=0-935702-75-X |year=1999 |publisher=University Science Books}}</ref>  Although the two words precision and accuracy can be [[synonymous]] in [[colloquial]] use, they are deliberately contrasted in the context of the [[scientific method]].

The field of [[statistics]], where the interpretation of measurements plays a central role, prefers to use the terms ''[[Bias (statistics)|bias]]'' and ''[[Variability (statistics)|variability]]'' instead of accuracy and precision: bias is the amount of inaccuracy and variability is the amount of imprecision.

A measurement system can be accurate but not precise, precise but not accurate, neither, or both. For example, if an experiment contains a [[systematic error]], then increasing the [[sample size]] generally increases precision but does not improve accuracy. The result would be a consistent yet inaccurate string of results from the flawed experiment.  Eliminating the systematic error improves accuracy but does not change precision.

A measurement system is considered ''valid'' if it is both ''accurate'' and ''precise''. Related terms include ''bias'' (non-[[random]] or directed effects caused by a factor or factors unrelated to the [[independent variable]]) and ''error'' (random variability).

The terminology is also applied to indirect measurements—that is, values obtained by a computational procedure from observed data.

In addition to accuracy and precision, measurements may also have a [[measurement resolution]], which is the smallest change in the underlying physical quantity that produces a response in the measurement.

In [[numerical analysis]], accuracy is also the nearness of a calculation to the true value; while precision is the resolution of the representation, typically defined by the number of decimal or binary digits.

In military terms, accuracy refers primarily to the accuracy of fire (''justesse de tir''), the precision of fire expressed by the closeness of a grouping of shots at and around the centre of the target.<ref>North Atlantic Treaty Organization, NATO Standardization Agency AAP-6 – Glossary of terms and definitions, p 43.</ref>