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Document Type

Research

Abstract

The reliability of a test is usually defined as the consistency with which a test measures whatever it measures, the consistency being indicated by the correlation between two administrations of the same test or between equivalent forms. Whenever it has not been feasible to administer the test twice, or whenever full-length equivalent forms have not been available, the procedure usually followed has been that of making two synthetic tests by scoring the odd- and even-numbered items separately, or by scoring two randomly-drawn lists of items. Dividing the test in this manner results in obtaining a correlation between two forms which are half the length of the original test. It has long been recognized that the reliability of a test is increased as its length is increased. Spearman (17) and Brown (1), in a formula developed independently, have expressed the degree of reliability to be expected by lengthening tests. When this formula is applied to the correlation obtained from two halves of a test, an estimation of the reliability to be expected by lengthening the tests is obtained.

Publication Date

1949

Journal Title

Proceedings of the Iowa Academy of Science

Volume

56

Issue

1

First Page

271

Last Page

277

Copyright

© Copyright 1949 by the Iowa Academy of Science, Inc.

Language

EN

File Format

application/pdf

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