Cited by 2,061Statistical Methods in EpidemiologyStatistical Methods and InferenceStatistical Methods and Applications

What you see may not be what you get: a brief, nontechnical introduction to overfitting in regression-type models

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Babyak, M. A.·2004·Psychosomatic Medicine

Abstract

OBJECTIVE: Statistical models, such as linear or logistic regression or survival analysis, are frequently used as a means to answer scientific questions in psychosomatic research. Many who use these techniques, however, apparently fail to appreciate fully the problem of overfitting, ie, capitalizing on the idiosyncrasies of the sample at hand. Overfitted models will fail to replicate in future samples, thus creating considerable uncertainty about the scientific merit of the finding. The present article is a nontechnical discussion of the concept of overfitting and is intended to be accessible to readers with varying levels of statistical expertise. The notion of overfitting is presented in terms of asking too much from the available data. Given a certain number of observations in a data set, there is an upper limit to the complexity of the model that can be derived with any acceptable degree of uncertainty. Complexity arises as a function of the number of degrees of freedom expended (the number of predictors including complex terms such as interactions and nonlinear terms) against the same data set during any stage of the data analysis. Theoretical and empirical evidence--with a special focus on the results of computer simulation studies--is presented to demonstrate the practical consequences of overfitting with respect to scientific inference. Three common practices--automated variable selection, pretesting of candidate predictors, and dichotomization of continuous variables--are shown to pose a considerable risk for spurious findings in models. The dilemma between overfitting and exploring candidate confounders is also discussed. Alternative means of guarding against overfitting are discussed, including variable aggregation and the fixing of coefficients a priori. Techniques that account and correct for complexity, including shrinkage and penalization, also are introduced.

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Crossref · 10.1097/01.psy.0000127692.23278.a9

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  • The finding that the changes in the mindfulness facets observation, acting with awareness, and non-reactivity to inner experience were no longer significant after including an additional, third, covariate could also be a consequence of a reduction in power or overfitting of the model.

    “The finding that the changes in the mindfulness facets observation, acting with awareness, and non-reactivity to inner experience were no longer significant after including an additional, third, covariate could also be a consequence of a reduction in power or overfitting of the model as in general, more observations per predictor lead to more reliable estimates (41).”
  • Regression models are increasingly prone to overfitting as the number of covariates increases.

    “While our consideration of multiple potential confounders is a strength, regression models are increasingly prone to overfitting as the number of covariates increases (Babyak, 2004).”

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Authors
Babyak, M. A.
Affiliations
Duke University (US)
Corresponding author
Babyak, M. A.
Venue
Psychosomatic Medicine
Published
2004-05-01
Volume
66
Issue
3
Pages
411-421
ISSN
  • 0033-3174 (ISSN-L)
  • 1534-7796
OpenAlex
W2165786903
Cited by
2,061
References
33
Citations by year
2026: 109 · 2025: 139 · 2024: 110 · 2023: 98 · 2022: 110 · 2021: 167 · 2020: 144 · 2019: 149 · 2018: 122 · 2017: 139 · 2016: 110 · 2015: 100 · 2014: 105 · 2013: 92 · 2012: 92
FWCI
16.88
Type
journal article
Language
en
Open access
Licence
cc-by-nc-nd
Locations
  • Psychosomatic Medicine (publishedVersion)
  • Psychosomatic Medicine (publishedVersion, cc-by-nc-nd)
  • PubMed (publishedVersion)
Topics
  • Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods in Epidemiology
  • Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods and Inference
  • Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods and Applications
Keywords
overfitting, regression models, model complexity, degrees of freedom, replication, variable aggregation, shrinkage, penalty method, spurious findings, psychosomatic research
MeSH terms
Computer Simulation, Data Interpretation, Statistical, Humans, Psychophysiology, Psychosomatic Medicine, Regression Analysis, Research Design, Statistics as Topic, Models, Statistical

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