The Kuder-Richardson coefficient (specifically KR-20 and KR-21) is used to estimate the internal consistency reliability of a test and is mathematically equivalent to the average of all possible split-half reliabilities. It is most often used with tests whose items are scored dichotomously (e.g., correct/incorrect). “Kuder-Richardson formulas provide an index of reliability that represents the average of all possible split-half coefficients for a test.”
[Reference: Helwig, A. A. (2020). CPCE Study Guide and Review; Cohen, R. J., & Swerdlik, M. E. (2018). Psychological Testing and Assessment., ]
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