Reliability refers the consistency of scores obtained by the same person when examine the same test on different occasions.

Reliability refers to the extent to which a test or other instrument is consistent in its measures. For example, a weight scale can be judged reliable if measures for a 25-pond weight do not vary over time or change for subsequence weightings.


Reliability is an important concept in science. If a test is not reliable, we cannot find the answer to our questions. Imagine placing a 25-pond weight on a scale and getting a different answer every time. What purpose would the scale serve?



In fact, we most likely would question in indeed the scale is measuring weight or something entirely different. Unreliability would prohibit us from reporting our findings simply because they are not reliable.

Effects of Errors

  1. Errors of measurement
  2. Errors of variance

Types of Reliability

    1. Test re test reliability
    1. Alternate/equalent form of reliability
  1. Split half reliability


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