Accuracy and Precision
Accuracy and Inaccuracy
The accuracy of a measurement is how close a result comes to the true value.
Systematic error or Inaccuracy is quantified by the average difference (bias) between a set of measurements obtained with the test method with a reference value or values obtained with a reference method.
Precision and Imprecision
Precision refers to how well measurements agree with each other in multiple tests.
Random error or Imprecision is usually quantified by calculating the coefficient of variation from the results of a set of duplicate measurements (Westgard, 2008).
|Accurate and Precise|
|Accurate but not Precise|
|Precise but not Accurate||Not Precise or Accurate|
- Westgard JO (2008) Basic method validation. 3rd ed. Madison: Westgard QC, Inc.