Repeatability

A desirable trait that occurs when the same person can get the same measurement result more than once.

Repeatability or other otherwise known as test-retest reliability is the variation in measurements if they would have been taken by a single person or instrument on the same item and under the same conditions. A less-than-perfect test-retest reliability causes test-retest variability. Such variability can be caused by, for example, intra-individual variability and intra-observer variability. A measurement may be said to be repeatable when this variation is smaller than some agreed limit.

Repeatability is practically used, for example, in medical monitoring of conditions. In these situations, there is often a predetermined "critical difference", and for differences in monitored values that are smaller than this critical difference, the possibility of pre-test variability as a sole cause of the difference may be considered in addition to, for examples, changes in diseases or treatments.

Repeatability can be defined with the following conditions:

* 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.