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On Accuracy in Reliability Estimation

Kristof, Walter
Publication Year:
Report Number:
ETS Research Bulletin
Document Type:
Page Count:
Subject/Key Words:
Evaluation, Psychometrics, Scores, Statistical Analysis, Test Reliability


This study in parametric test theory deals with the statistics of reliability estimation when scores on two parts of a test follow a binormal distribution with equal (case 1) or unequal (case 2) expectations. In each case biased maximum likelihood estimators of reliability are obtained and converted into unbiased eimators. Sampling distributions are derived. Second moments are obtained and utilized in calculating mean square errors of estimation as a measure of accuracy. A rank order of four estimators is established. There is a uniformly best estimator. Tables of absolute and relative accuracies are provided for various reliability parameters and sample sizes. (Author) (12pp.)

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