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Peer reviewedFeldt, Leonard S. – Educational and Psychological Measurement, 1984
The binomial error model includes form-to-form difficulty differences as error variance and leads to Ruder-Richardson formula 21 as an estimate of reliability. If the form-to-form component is removed from the estimate of error variance, the binomial model leads to KR 20 as the reliability estimate. (Author/BW)
Descriptors: Achievement Tests, Difficulty Level, Error of Measurement, Mathematical Formulas
