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Repeatability or test–retest reliability〔(Types of Reliability ) The Research Methods Knowledge Base. Last Revised: 20 October 2006〕 is the variation in measurements taken by a single person or instrument on the same item, under the same conditions, and in a short period of time. 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 a pre-determined acceptance criteria. Test–retest variability 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. ==Establishment== According to the ''Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results'', the following conditions need to be fulfilled in the establishment of repeatability: *the same experimental tools *the same observer *the same measuring instrument, used under the same conditions *the same location *repetition over a short period of time. *same objectives Repeatability methods were developed by Bland and Altman (1986).〔http://www-users.york.ac.uk/~mb55/meas/ba.htm〕 If the correlation between separate administrations of the test is high (e.g. 0.7 or higher as in this Cronbach's alpha-internal consistency-table〔George, D., & Mallery, P. (2003). SPSS for Windows step by step: A simple guide and reference. 11.0 update (4th ed.). Boston: Allyn & Bacon.〕), then it has good test–retest reliability. The repeatability coefficient is a precision measure which represents the value below which the absolute difference between two repeated test results may be expected to lie with a probability of 95%. The standard deviation under repeatability conditions is part of precision and accuracy. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Repeatability」の詳細全文を読む スポンサード リンク
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