The quantitative treatment of data for theoretical or practical purposes requires a knowledge of the reliability and validity of the measures used. Bound up closely with these two problems is that of the objectivity of the measures. The validity of a measure is affected by its reliability, and its reliability is in turn affected by the subjectivity of the measures. The problem of validity will not be dealt with here. Our problem is to devise a criterion for comparable tests and to examine the various coefficients proposed as measures of reliability for a test.The reliability of a test has been defined by Ruch and Stoddard 1 as "the accuracy with which the test measures what it does measure." Kelley 2 attaches a similar meaning to the reliability coefficient, although he injects into his argument certain concepts which the writer believes to belong essentially under validity. Kelley's views on the subject are illustrated by the following quotations:
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