What is the difference between accuracy and precision?

Document ID

Document ID TE783

Published Date

Published Date 27/05/2017
Question
What is the difference between accuracy and precision?
Summary
Difference between accuracy and precision
Answer
Accuracy refers to how close a result is to the true value. Precision refers to how repeatable the result is using fresh portions of the same sample. Although good precision suggests good accuracy, precise results can be inaccurate. For example, a result of 1.0 mg/L using a 1.0 mg/L standard solution is a very accurate result. Results of 1.73 mg/L, 1.74 mg/L, and 1.75 mg/L using a 1.0 mg/L standard solution shows good precision, but poor accuracy. The best way to check accuracy and precision is to use a standard solution that has a known concentration. If the results using a standard are close to the standard concentration, the result is accurate. If repeating the test several times with fresh portions of the standard and provides similar results, the results are precise.