Repeatability

Repeatability is the variation in measurements taken by a single person or instrument on the same item and under the same conditions. A measurement may be said to be repeatable when this variation is smaller than some agreed limit. According to the Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results, repeatability conditions include:


 * the same measurement procedure
 * the same observer
 * the same measuring instrument, used under the same conditions
 * the same location
 * repetition over a short period of time.

The standard deviation under repeatability conditions is often used as a measure of precision, although it should be noted that "precision" is most often used qualitatively.