RELIABILITY IN STATISTICS Reliability (statistics) From Wikipedia, the free encyclopedia In statistics, reliability is the consistency of a set of measurements or measuring instrument, often used to describe a test. This can either be whether the measurements of the same instrument give or are likely to give the same measurement (test-retest), or in the case of more subjective instruments, such as personality or trait inventories, whether two independent assessors give similar scores (inter-rater reliability). Reliability is inversely related to random error. Reliability does not imply validity. That is, a reliable measure is measuring something consistently, but not necessarily what it is supposed to be measuring. For example, while there are many reliable tests of specific abilities, not all of them would be valid for predicting, say, job performance. In terms of accuracy and precision, reliability is precision, while validity is accuracy. In experimental sciences, reliability is the extent to which the measurements of a test remain consistent over repeated tests of the same subject under identical conditions. An experiment is reliable if it yields consistent results of the same measure. It is unreliable if repeated measurements give different results. It can also be interpreted as the lack of random error in measurement.[1] In engineering, reliability is the ability of a system or component to perform its required functions under stated conditions for a specified period of time. It is often reported in terms of a probability. Evaluations of reliability involve the use of many statistical tools. See Reliability engineering for further discussion. An example often used to illustrate the difference between reliability and validity in the experimental sciences involves a common bathroom scale. If someone that weighs 200 lbs. steps on the scale 10 times, and it reads 200 each time, then the measurement is reliable and valid. If the scale consistently reads 150, then it is not valid, but it is still reliable because the measurement is very consistent. If the scale varied a lot around 200 (190, 205, 192, 209, etc.), then the scale could be considered valid but not reliable.
Posted on: Sat, 10 Jan 2015 15:37:55 +0000
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