ERIC Number: EJ741008
Record Type: Journal
Publication Date: 2006
Robust Confidence Interval for a Ratio of Standard Deviations
Bonett, Douglas G.
Applied Psychological Measurement, v30 n5 p432-439 2006
Comparing variability of test scores across alternate forms, test conditions, or subpopulations is a fundamental problem in psychometrics. A confidence interval for a ratio of standard deviations is proposed that performs as well as the classic method with normal distributions and performs dramatically better with nonnormal distributions. A simple and accurate sample size planning formula is proposed for estimating a ratio of standard deviations with desired confidence and precision. (Contains 5 tables.)
Descriptors: Intervals, Mathematical Concepts, Comparative Analysis, Psychometrics, Robustness (Statistics), Statistical Distributions, Sample Size, Scoring Formulas, Information Retrieval, Hypothesis Testing, Simulation, Probability
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Publication Type: Journal Articles; Reports - Research
Education Level: N/A
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