SMOTE: Synthetic Minority Over-sampling Technique
Written for the Research library (claude-opus-5-5) from the paper text. Original — jair.org/index.php/jair/article/download/10302/24590
Summary
Many real-world classification tasks have heavily skewed class distributions. Examples include fraud detection, oil-spill detection in satellite images and mammogram pixel classification, where the rare class is usually the one that matters. Plain accuracy hides poor minority-class detection, so the authors evaluate with ROC analysis, AUC and the ROC convex hull. They propose SMOTE, which expands the minority class with artificial examples rather than duplicates. Each new example is interpolated between a minority sample and one of its nearest minority-class neighbours in feature space. SMOTE is combined with random under-sampling of the majority class. It is tested with C4.5, Ripper and Naive Bayes on datasets that differ in size and degree of imbalance. Across nearly all settings, the combination dominates under-sampling alone, Ripper's loss-ratio tuning and Naive Bayes prior adjustment in ROC space. The authors argue this works because synthetic points push learners toward broader minority decision regions. Replication tends to make those regions narrower and overfitted. The work is a foundational resampling baseline for imbalanced learning.
Key points
- SMOTE creates new minority examples along line segments joining existing minority points and their nearest minority neighbours. It is paired with majority-class under-sampling.
- The baselines are under-sampling only (e.g., Under-C4.5, Under-Ripper), varied loss ratios in Ripper and varied class priors in Naive Bayes. All comparisons use AUC and the ROC convex hull.
- SMOTE-based classifiers were best in all but 4 of 48 experiments:
- Naive Bayes won on Pima, the least imbalanced dataset.
- Under-Ripper beat SMOTE-Ripper on Oil.
- The curves overlapped on Can.
- Other datasets mentioned include Satimage and a mammography set (about 98% normal vs. 2% abnormal pixels).
- Proposed extensions include SMOTE-N, which builds synthetic nominal feature values by majority vote among neighbours. The authors also suggest applying SMOTE to information retrieval with bag-of-words features and feature selection.
Cited by
- A Survey of Data Augmentation Approaches for NLP
- SemEval-2018 Task 3: Irony Detection in English Tweets
- mixup: Beyond Empirical Risk Minimization
Cite
@article{chawla2002smote,
title = {{SMOTE: Synthetic Minority Over-sampling Technique}},
author = {Chawla, Nitesh V. and Bowyer, Kevin W. and Hall, Lawrence and Kegelmeyer, W. Philip},
journal = {Journal of Artificial Intelligence Research},
year = {2002},
doi = {10.1613/jair.953},
url = {https://doi.org/10.1613/jair.953}
}References
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