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Statistically Significant Linear Regression Coefficients Solely Driven By Outliers In Finite-sample Inference

Felix Reichel

arXiv 15 May 2025 · Statistics — Methodology · publishedQeios (2025) · 1 citations (OpenAlex)

arXiv:2505.10738 · PDF · DOI · OpenAlex · Extracted main text

Abstract

In this paper, we investigate the impact of outliers on the statistical significance of coefficients in linear regression. We demonstrate, through numerical simulation using R, that a single outlier can cause an otherwise insignificant coefficient to appear statistically significant. We compare this with robust Huber regression, which reduces the effects of outliers. Afterwards, we approximate the influence of a single outlier on estimated regression coefficients and discuss common diagnostic statistics to detect influential observations in regression (e.g., studentized residuals). Furthermore, we relate this issue to the optional normality assumption in simple linear regression [14], required for exact finite-sample inference but asymptotically justified for large n by the Central Limit Theorem (CLT). We also address the general dangers of relying solely on p-values without performing adequate regression diagnostics. Finally, we provide a brief overview of regression methods and discuss how they relate to the assumptions of the Gauss-Markov theorem.

Citation extraction

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Most heavily cited references

The works this paper leans on most, across its whole bibliography — not restricted to papers in our corpus. Ranked by composite intensity, which combines how often a work is mentioned, how many sections mention it, and how much of that falls in the main text rather than the appendix.

ReferenceIntensityMentionsSectionsMain text
1Jeffrey M. Wooldridge (2019) Introductory Econometrics: A Modern Approach0.87472100%
2Peter J. Huber (1964) Robust estimation of a location parameter0.84333100%
3David A. Belsley, Edwin Kuh, and Roy E. Welsch (1980) Regression Diagnostics: Identifying Influential Data and Sources of Collinearity0.73732100%
4Tobias E. Ugah, Emmanuel I. Mba, Micheal C. Eze, Kingsley C. Arum, I… (2021) On the upper bounds of test statistics for a single outlier test in linear regression models0.64422100%
5R. Dennis Cook (1977) Detection of influential observations in linear regression0.64422100%
6Amand F. Schmidt and Chris Finan (2018) Linear regression and the normality assumption0.40511100%
7Vic Barnett and Toby Lewis (1978) Outliers in Statistical Data0.40511100%
8William S. Cleveland (1979) Robust locally weighted regression and smoothing scatterplots0.40511100%
9P. J. Cornbleet and N. Gochman (1989) Incorrect least-squares regression coefficients in method-comparison analysis0.40511100%
10Carl de Boor (1978) A Practical Guide to Splines0.40511100%

Showing the top 10 of 20 scored citations.