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An Index of the Discriminating Power of a Test at Different Parts of the Score Range

Author(s):
Levine, Richard S.; Lord, Frederic M.
Publication Year:
1958
Report Number:
RB-58-13
Source:
ETS Research Bulletin
Document Type:
Report
Page Count:
10
Subject/Key Words:
Discrimination Index, Scores, Statistical Distributions, Test Reliability, Test Theory, Test Validity

Abstract

An important characteristic of any test is its ability to discriminate among examinees who differ in ability. The conventional reliability and validity coefficients are indices of discrimination for the test as a whole; however, except under certain limited conditions, these over-all indices do not apply at all points along the score scale. The purpose of the present paper is to provide such an index and illustrate its use.

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