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An Empirical Study of the Normality and Independence of Errors of Measurement in Test Scores

Lord, Frederic M.
Publication Year:
Report Number:
ETS Research Bulletin
Document Type:
Page Count:
Subject/Key Words:
Office of Naval Research, Error of Measurement, Statistical Distributions, Test Theory, True Scores


An empirical study is described for determining whether in actual practice the errors of measurement in a test score (a) are distributed normally and (b) independently of the true score. Standard error formulas are given for making the necessary significance tests. The results show that the variance of the errors of measurement was significantly associated with true score in each of the four groups studied, and that the distribution of the errors of measurement was significantly skewed in three of these four groups.

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