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The Kuder and Richardson Formula 20 (KR-20), published in 1937, checks the internal consistency of items on a test. The internal consistency, or reliability, refers to the degree to which all of the test items measure a common characteristic of the examinees and are free from measurement error, which can be random (e.g., an examinee’s mood or health condition) or systematic (e.g., the sound of traffic outside). As an indicator of stability of performance, reliability is desired in any test. This entry defines and explains how to interpret the KR-20, describes its applications and limitations, and provides an example of calculating the KR-20 statistic using the software program SPSS.

Definition and Interpretation

The KR-20 is a special case of Cronbach’s α in which the items are binary ...

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