Evaluating Stratification Alternatives to Improve Software Defect Prediction
Bibliographic record
Abstract
Numerous studies have applied machine learning to the software defect prediction problem, i.e. predicting which modules will experience a failure during operation based on software metrics. However, skewness in defect-prediction datasets can mean that the resulting classifiers often predict the faulty (minority) class less accurately. This problem is well known in machine learning, and is often referred to as “learning from imbalanced datasets.” One common approach for mitigating skewness is to use stratification to homogenize class distributions; however, it is unclear what stratification techniques are most effective, both generally and specifically in software defect prediction. In this article, we investigate two major stratification alternatives (under-, and over-sampling) for software defect prediction using Analysis of Variance. Our analysis covers several modern software defect prediction datasets using a factorial design. We find that the main effect of under-sampling is significant at α = 0.05, as is the interaction between under- and over-sampling. However, the main effect of over-sampling is not significant.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.035 | 0.094 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.002 | 0.001 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.003 |
| Open science | 0.001 | 0.002 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".