Accuracy
Definition and meaning of Accuracy in chemistry.
Accuracy is the degree to which a measured value agrees with the true or accepted value of a quantity. A result is accurate when it lies close to the correct value.
In more detail
Accuracy is distinct from precision, which describes how close repeated measurements are to one another. A set of measurements can be precise (tightly clustered) yet inaccurate if they are all shifted from the true value by a systematic error. Good accuracy therefore depends on proper calibration and on removing systematic errors from a method or instrument.
Key facts
| Definition | Closeness to the true or accepted value |
|---|---|
| Depends on | Calibration and removal of systematic error |
| Differs from | Precision (repeatability) |
| Field | Analytical Chemistry |
If a standard solution is known to be 100 ppm and a method gives readings of 99, 100, and 101 ppm, the results are both accurate and precise.
Frequently asked questions
What is the difference between accuracy and precision?
Accuracy measures how close a result is to the true value; precision measures how close repeated measurements are to each other. A measurement can be one without the other.
What reduces the accuracy of a measurement?
Systematic errors such as a poorly calibrated instrument, instrument drift, or a biased method all reduce accuracy.