The difference between accuracy and precision lies in what aspect of measurement they describe:
- Accuracy refers to how close a measurement or set of measurements is to the true or accepted value. It indicates correctness or truthfulness of the measurement. For example, if you are aiming for a target value, accuracy means hitting close to that target
- Precision refers to how close repeated measurements are to each other, regardless of whether they are close to the true value. It indicates consistency or repeatability of the measurements. You can have precise measurements that are all clustered together but far from the true value
In simpler terms, accuracy is about hitting the bullseye (true value), while precision is about grouping your darts closely together, whether or not they hit the bullseye
. A measurement system can be:
- Accurate but not precise (close to true value but results vary widely),
- Precise but not accurate (results tightly grouped but far from true value),
- Both accurate and precise (results tightly grouped near true value),
- Or neither (results scattered and far from true value)
Thus, accuracy measures correctness, and precision measures consistency.
Example: If a scale consistently shows 23.1 kg for a 20 kg weight, it is precise but not accurate. If it shows varying values around 20 kg, it may be accurate on average but not precise
This distinction is important in science, engineering, and statistics to understand measurement quality and error types
