Journal of Advances in Developmental Research
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Volume 17 Issue 1
2026
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Operationalizing Imbalance: Boundary vs. Density-Based Sampling in Extreme and Moderate Credit Risk Scenarios
| Author(s) | Sai Prashanth Pathi |
|---|---|
| Country | United States |
| Abstract | Machine learning models in credit risk are frequently compromised by the class imbalance problem, where fraud cases or defaults represent a negligible fraction of the population. While the Synthetic Minority Over-sampling Technique (SMOTE) is the de facto standard for addressing this, recent literature suggests it may introduce noise and computational overhead without operational gain. This study conducts a rigorous comparative analysis of six strategies: Cost-Sensitive Learning (Baseline), Random Undersampling (RUS), Vanilla SMOTE, Borderline-SMOTE, ADASYN, and SMOTE-ENN applied to Gradient Boosted Decision Trees (XGBoost). The evaluation utilizes three datasets with varying imbalance ratios (from 0.17% to 6.9%) to test robustness across different financial contexts. Our experiments reveal two critical insights. First, we identify a "False Positive Trap" in extreme imbalance scenarios: while Vanilla SMOTE achieved the highest Area Under Precision-Recall Curve (AUPRC: 0.825), it degraded the F1-score to 0.282, rendering it operationally inviable. In contrast, Borderline-SMOTE maintained a comparable AUPRC (0.818) while achieving a superior F1-score (0.690). Second, we detect a "Threshold of Necessity": in scenarios with moderate imbalance (>5%), all sampling techniques failed to outperform the cost-sensitive baseline, suggesting that synthetic sampling is counter-productive when sufficient minority examples exist. |
| Keywords | Credit Risk, Class Imbalance, Fraud Detection, XGBoost, SMOTE, Anomaly Detection. |
| Field | Engineering |
| Published In | Volume 16, Issue 2, July-December 2025 |
| Published On | 2025-12-12 |
| Cite This | Operationalizing Imbalance: Boundary vs. Density-Based Sampling in Extreme and Moderate Credit Risk Scenarios - Sai Prashanth Pathi - IJAIDR Volume 16, Issue 2, July-December 2025. DOI 10.71097/IJAIDR.v16.i2.1691 |
| DOI | https://doi.org/10.71097/IJAIDR.v16.i2.1691 |
| Short DOI | https://doi.org/hbphzs |
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