Balancing the Scales: A Theoretical and Algorithmic Framework for Learning from Imbalanced Data

Fuente: arXiv
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Autores principales: Cortes, Corinna, Mao, Anqi, Mohri, Mehryar, Zhong, Yutao
Formato: Preprint
Publicado: 2025
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author Cortes, Corinna
Mao, Anqi
Mohri, Mehryar
Zhong, Yutao
author_facet Cortes, Corinna
Mao, Anqi
Mohri, Mehryar
Zhong, Yutao
contents Class imbalance remains a major challenge in machine learning, especially in multi-class problems with long-tailed distributions. Existing methods, such as data resampling, cost-sensitive techniques, and logistic loss modifications, though popular and often effective, lack solid theoretical foundations. As an example, we demonstrate that cost-sensitive methods are not Bayes-consistent. This paper introduces a novel theoretical framework for analyzing generalization in imbalanced classification. We propose a new class-imbalanced margin loss function for both binary and multi-class settings, prove its strong $H$-consistency, and derive corresponding learning guarantees based on empirical loss and a new notion of class-sensitive Rademacher complexity. Leveraging these theoretical results, we devise novel and general learning algorithms, IMMAX (Imbalanced Margin Maximization), which incorporate confidence margins and are applicable to various hypothesis sets. While our focus is theoretical, we also present extensive empirical results demonstrating the effectiveness of our algorithms compared to existing baselines.
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publishDate 2025
record_format arxiv
spellingShingle Balancing the Scales: A Theoretical and Algorithmic Framework for Learning from Imbalanced Data
Cortes, Corinna
Mao, Anqi
Mohri, Mehryar
Zhong, Yutao
Machine Learning
Class imbalance remains a major challenge in machine learning, especially in multi-class problems with long-tailed distributions. Existing methods, such as data resampling, cost-sensitive techniques, and logistic loss modifications, though popular and often effective, lack solid theoretical foundations. As an example, we demonstrate that cost-sensitive methods are not Bayes-consistent. This paper introduces a novel theoretical framework for analyzing generalization in imbalanced classification. We propose a new class-imbalanced margin loss function for both binary and multi-class settings, prove its strong $H$-consistency, and derive corresponding learning guarantees based on empirical loss and a new notion of class-sensitive Rademacher complexity. Leveraging these theoretical results, we devise novel and general learning algorithms, IMMAX (Imbalanced Margin Maximization), which incorporate confidence margins and are applicable to various hypothesis sets. While our focus is theoretical, we also present extensive empirical results demonstrating the effectiveness of our algorithms compared to existing baselines.
title Balancing the Scales: A Theoretical and Algorithmic Framework for Learning from Imbalanced Data
topic Machine Learning
url https://arxiv.org/abs/2502.10381