Resampling strategies for machine learning-based effort overrun risk detection: A controlled factorial study with cost-sensitive evaluation
The Synthetic Minority Oversampling Technique (SMOTE) has become the default preprocessing step for handling class imbalance in software effort-risk prediction, yet its effectiveness in this domain has not been rigorously tested. This study addresses that gap through a controlled factorial experiment on the publicly available Software Development Effort Dataset Annotated with Expert Estimates dataset, comprising 4,329 software issues from Apache projects drawn from an initial repository of 23,186 records. Six resampling strategies are compared across four classifier families under both standard and cost-sensitive evaluation metrics that weight missed high-risk issues more heavily than false alarms. A secondary contribution is the analysis of how resampling interacts with the extreme class imbalance characteristic of real-world effort data (2.2% minority rate), a regime substantially more severe than those examined in prior investigations. Results are interpreted through SHAP-based feature attribution to determine whether oversampling alters which features the models rely on. The findings reveal two overarching results: near-perfect performance under a full feature set is largely attributable to target leakage rather than a genuine predictive signal, and, under deployment, valid early-warning features degrade cost-sensitive performance relative to no resampling when SMOTE is used. Cost-sensitive weighting emerges as the more reliable alternative, preserving both performance and feature attribution structure. These findings challenge the uncritical adoption of SMOTE in software analytics and carry direct implications for the design of reproducible, interpretable risk-detection pipelines.