1. n. [Formation Evaluation]

The closeness of agreement between independent results obtained in the normal and correct operation of the same method on identical test material, in a short space of time, and under the same test conditions (such as the same operator, same apparatus, same laboratory). (ISO) The repeatability of core and log measurements can be checked properly in the laboratory. The repeatability of a downhole log is checked by recording a repeat section (or repeat stations for stationary measurements). The term repeatability is used even though it is not possible to ensure that the same test material is used. On two separate runs, the tool may not take the same path in the borehole, and therefore may not measure the same volume of formation.

See related terms: accuracy,  precision,  reproducibility,  uncertainty

2. n. [Formation Evaluation]

The representative parameters of the dispersion of the population that may be associated with the results are qualified by the term repeatability, for example "repeatability standard deviation," or "repeatability variance." (ISO)

3. n. [Formation Evaluation]

The quantitative value that is equal to or below the absolute difference between two test results, within a probability of 95%. (ISO) In a test of repeatability, the results are obtained independently by the normal and correct operation of the same method on identical test material, in a short space of time, and under the same test conditions (such as the same operator, same apparatus, same laboratory).