Glossary · Sensors and measurement
Precision
Also known as: Measurement precision
German: Präzision
In metrology, precision (measurement precision) is the closeness of agreement between measured values obtained by replicate measurements on the same or similar objects under specified conditions. It is expressed by measures of dispersion such as the standard deviation.
- Sensors
- Standards
In one sentence
Precision is the closeness of repeated measurements to each other under specified conditions, expressed e.g. as a standard deviation.
Example
Ten measurements of the same shaft diameter vary by only 2 µm, so the gauge is precise, but calibration shows a constant 10 µm offset.
How it applies
- Engineering: Precision is specified for defined conditions: Repeatability for the same operator, instrument and short time; reproducibility for changed conditions such as different operators or locations.
- Quality: Measurement system analysis evaluates precision before a measuring system is used to control a process or accept parts.
- Operation: A precise but inaccurate instrument can be corrected by calibration; an imprecise one cannot, because its scatter remains.
- Documentation: Do not use precise as a synonym for accurate in manuals and marketing texts. State which property is meant and the conditions.
Precision vs. accuracy
Precision is about scatter; Accuracy is about closeness to the true value. In German, Präzision and Genauigkeit are also often confused, so translation should keep them apart.