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Sample Size Requirements for Precise Estimates of Reliability, Generalizability, and Validity Coefficients
Precision of the reliability coefficient (r) is investigated. The width of the confidence interval for r as a function of sample size (N) is shown for retest, alternate-form, split-half, alpha, intraclass, interrater, and validity coefficients. Although the determination of the N needed for reliabil...
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Published in: | Journal of clinical and experimental neuropsychology 1999-08, Vol.21 (4), p.559-566 |
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Main Author: | |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that cite this one |
Online Access: | Get full text |
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Summary: | Precision of the reliability coefficient (r) is investigated. The width of the confidence interval for r as a function of sample size (N) is shown for retest, alternate-form, split-half, alpha, intraclass, interrater, and validity coefficients. Although the determination of the N needed for reliability studies is somewhat subjective, a minimum of 400 subjects is recommended. Much larger N s may be needed for validity studies. A survey of published reliability studies shows that 59% of the sample sizes were less than 100. Confidence intervals for obtained test scores are used as a practical application measure that also leads to the conclusion of a minimum of 400 subjects. |
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ISSN: | 1380-3395 1744-411X |
DOI: | 10.1076/jcen.21.4.559.889 |