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The Cost of Dichotomization
Open accessAbstract
Assuming bivariate normality with correlation r, dichotomizing one variable at the mean results in the reduction in variance accounted for to .647r²; and dichotomizing both at the mean, to .405r². These losses, in turn, result in reduction in statistical power equivalent to discarding 38% and 60% of the cases under representative conditions. As dichotomization departs from the mean, the costs in variance accounted for and in power are even larger. Consequences of this practice in measurement applications are considered. These losses may not be quite so large in real data, but since methods are available for making use of all the original scaling information, there is no reason to sustain them.
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“However, grouping loses information and may reduce statistical power [ 87 ] especially when dichotomization is used [ 82 , 85 , 88 ].”
From Strengthening the Reporting of Observational Studies in Epidemiology (STROBE): Explanation and Elaboration (2007) · cites this paper as [87]
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Metadata
- Authors
- Cohen, J.
- Affiliations
- New York University (US)
- Corresponding author
- Cohen, Jacob
- Venue
- Applied Psychological Measurement
- Publisher
- SAGE Publications
- Published
- 1983-06
- Volume
- 7
- Issue
- 3
- Pages
- 249-253
- ISSN
- 0146-6216 (ISSN-L)
- 1552-3497
- OpenAlex
- W1987838173
- Cited by
- 1,564
- References
- 0
- Citations by year
- 2026: 67 · 2025: 59 · 2024: 59 · 2023: 50 · 2022: 63 · 2021: 66 · 2020: 74 · 2019: 68 · 2018: 91 · 2017: 78 · 2016: 66 · 2015: 79 · 2014: 86 · 2013: 53 · 2012: 60
- FWCI
- 3.58
- Type
- journal article
- Language
- en
- Open access
- green
- purl.umn.edu
- Locations
- Applied Psychological Measurement (publishedVersion)
- University of Minnesota Digital Conservancy (University of Minnesota) (submittedVersion)
- Topics
- Social Sciences › Decision Sciences › Management Science and Operations Research › Psychometric Methodologies and Testing
- Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods and Applications
- Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods and Bayesian Inference
- Keywords
- dichotomization, variable reduction, bivariate normal distribution, correlation, variance accounted for, statistical power, measurement loss, scale reduction
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