repeatabilità

Repeatability is the degree to which successive measurements of the same quantity, carried out under identical conditions, yield the same result. In metrology and quality control, it reflects the precision of a measurement procedure when the same operator uses the same instrument, on the same item, in a short time frame. It is often quantified by the standard deviation of repeated measurements or by a repeatability limit, which defines the range within which most repeated results fall.

Repeatability is distinct from reproducibility. Reproducibility assesses variation when measurements are made under changed conditions, such as different operators, different instruments, or different laboratories. Together, repeatability and reproducibility form components of measurement system analysis and contribute to overall measurement uncertainty.

Causes of limited repeatability include instrument noise, small fluctuations in the measurement process, operator technique, and environmental conditions. Improving repeatability involves standardizing procedures, regular calibration and maintenance of instruments, environmental control, operator training, and, in some cases, automation or using higher-precision equipment.

In practice, repeatability is used to assess whether a measurement process is sufficiently precise for its intended purpose. It informs quality control decisions, method validation, and troubleshooting. The concept is closely linked to accuracy and uncertainty: repeatability concerns the consistency (precision) of measurements under fixed conditions, while accuracy involves closeness to a true value, and uncertainty combines multiple sources of error, including repeatability.