Accuracy vs Precision - Difference and Comparison

Also Compare

Cameras Cars Cell Phones GPS Systems Processors Tennis Players more..

From Diffen

[Edit Comparison Table]

Similarities (2)

Differences (3)

Show All (5)

	Accuracy	Precision
Uses:	Physics, engineering, statistics etc.	Physics, engineering, statistics etc.
About:	A term used in measuring something	A term used in measuring something
Definition:	The accuracy of an experiment/object/value is a measure of how closely the experimental results agree with a true or accepted value.	precision of an experiment/object/value is a measure of the reliability of the experiment, or how reproducible the experiment is
Measurements:	Single	A number of measurements are needed
Quality:	Doesn't speak of quality	Speaks of quality of product

Both accuracy and precision are terms used in the fields of science, engineering and statistics. While accuracy is the degree of conformity of a measured or calculated quantity to its actual (true) value, precision is the degree to which further measurements or calculations show the same or similar results.

1 About
2 Example
3 Target comparison
4 Number of measurements
5 Quality
6 Uses
7 References

[edit] About

Accuracy and precision are used in context to measuring an object. An example can be: 3.14 is an accurate value of pie, but it is not precise. 3.1415 may be more precise. The precision of an experiment/object/value is a measure of the reliability of the experiment, or how reproducible the experiment is. The accuracy of an experiment/object/value is a measure of how closely the experimental results agree with a true or accepted value.

[edit] Example

One can say that a measurement is accurate but not precise; precise but not accurate; neither or both. An example of bad precision and good accuracy can be: Suppose a lab refrigerator holds a constant temperature of 38.0 F. A temperature sensor is tested 10 times in the refrigerator. The temperatures from the test yield the temperatures of: 37.8, 38.3, 38.1, 38.0, 37.6, 38.2, 38.0, 38.0, 37.4, 38.3. This distribution shows no impressive tendency toward a particular value (lack of precision) but each value does come close to the actual temperature (high accuracy).

[edit] Target comparison

Accuracy is the degree of veracity while precision is the degree of reproducibility. Target comparison can be used to explain this difference between the two terms. If arrows are fired at a target and measurements are taken then accuracy will describe the closeness of the arrows to the bullseye at the target center. Arrows that strike closer to the bullseye are considered more accurate. The closer a system's measurements to the accepted value, the more accurate the system is considered to be. If a large number of arrows are fired, precision would be the size of the arrow cluster. (When only one arrow is fired, precision is the size of the cluster one would expect if this were repeated many times under the same conditions.) When all arrows are grouped tightly together, the cluster is considered precise since they all struck close to the same spot, if not necessarily near the bullseye. The measurements are precise, though not necessarily accurate. However, it is not possible to reliably achieve accuracy in individual measurements without precision.

[edit] Number of measurements

Another difference between the two can be that accuracy can be determined by one measurement while many measurements are needed to determine precision. In the above example, by just one arrow fired, one knows if it is accurate or no but a number of arrows have to be fired to know if the result is precise or no.

[edit] Quality

While a precise measurement may speak highly of an instruments quality, an accurate reading will not reflect on the quality. Accuracy is an agreement of a measured value with an expected value. Another example: A stopped clock will be accurate twice in day, but it will not be precise - a reflection on its quality. If a clock reflects the right time in 10 readings at noon for 10 days, it can be considered precise and therefore quality.