Cited by 3,088Imbalanced Data Classification TechniquesAdvanced Neural Network ApplicationsMachine Learning and Data Classification

A systematic study of the class imbalance problem in convolutional neural networks

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Buda, Mateusz, Maki, Atsuto, Mazurowski, Maciej A.·2018·Neural Networks

Abstract

In this study, we systematically investigate the impact of class imbalance on classification performance of convolutional neural networks (CNNs) and compare frequently used methods to address the issue. Class imbalance is a common problem that has been comprehensively studied in classical machine learning, yet very limited systematic research is available in the context of deep learning. In our study, we use three benchmark datasets of increasing complexity, MNIST, CIFAR-10 and ImageNet, to investigate the effects of imbalance on classification and perform an extensive comparison of several methods to address the issue: oversampling, undersampling, two-phase training, and thresholding that compensates for prior class probabilities. Our main evaluation metric is area under the receiver operating characteristic curve (ROC AUC) adjusted to multi-class tasks since overall accuracy metric is associated with notable difficulties in the context of imbalanced data. Based on results from our experiments we conclude that (i) the effect of class imbalance on classification performance is detrimental; (ii) the method of addressing class imbalance that emerged as dominant in almost all analyzed scenarios was oversampling; (iii) oversampling should be applied to the level that completely eliminates the imbalance, whereas the optimal undersampling ratio depends on the extent of imbalance; (iv) as opposed to some classical machine learning models, oversampling does not cause overfitting of CNNs; (v) thresholding should be applied to compensate for prior class probabilities when overall number of properly classified cases is of interest.

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Crossref · 10.1016/j.neunet.2018.07.011

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Authors
Buda, M., Maki, A., & Mazurowski, M. A.
Affiliations
  • Duke University (US)
  • KTH Royal Institute of Technology (SE)
Corresponding author
Buda, Mateusz
Venue
Neural Networks
Publisher
Elsevier BV
Published
2018-10
Volume
106
Pages
249-259
ISSN
0893-6080 (ISSN-L)
OpenAlex
W2767106145
Cited by
3,088
References
83
Citations by year
2026: 459 · 2025: 507 · 2024: 371 · 2023: 405 · 2022: 405 · 2021: 380 · 2020: 308 · 2019: 189 · 2018: 58 · 2017: 5
FWCI
131.58
Type
journal article
Language
en
Open access
Locations
  • Neural Networks (publishedVersion)
  • PubMed (publishedVersion)
  • arXiv (Cornell University) (submittedVersion)
  • KTH Publication Database DiVA (KTH Royal Institute of Technology) (submittedVersion, other-oa)
  • arXiv (Cornell University)
Topics
  • Physical Sciences › Computer Science › Artificial Intelligence › Imbalanced Data Classification Techniques
  • Physical Sciences › Computer Science › Computer Vision and Pattern Recognition › Advanced Neural Network Applications
  • Physical Sciences › Computer Science › Artificial Intelligence › Machine Learning and Data Classification
Keywords
class imbalance, convolutional neural networks, oversampling, undersampling, two-stage training, thresholding, area under the receiver operating characteristic, multi-class classification, overfitting, MNIST, CIFAR-10, ImageNet
MeSH terms
Machine Learning, Humans, Probability, ROC Curve, Neural Networks, Computer

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