Machine Learning Model Validation for Early Stage Studies with Small Sample Sizes
Bibliographic record
Abstract
In early stage biomedical studies, small datasets are common due to the high cost and difficulty of sample collection with human subjects. This complicates the validation of machine learning models, which are best suited for large datasets. In this work, we examined feature selection techniques, validation frameworks, and learning curve fitting for small simulated datasets with known underlying discriminability, with the aim of identifying a protocol for estimating and interpreting early stage model performance and for planning future studies. Of a variety of examined validation configurations, a nested cross-validation framework provided the most accurate reflection of the selected features' discriminability, but the relevant features were often not properly identified during the feature selection stage for datasets with small sample sizes. Ultimately, we recommend that: (1) filter-based feature selection methods should be used to minimize overfitting to noise-based features, (2) statistical exploration should be conducted on datasets as a whole to estimate the level of discriminability and the feasibility of the classification problems, and (3) learning curves should be employed using nested cross-validation performance estimates for forecasting accuracy at larger sample sizes and estimating the required number of samples to converge towards best performance. This work should serve as a guideline for researchers incorporating machine learning in small-scale pilot studies.
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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 | 0.261 | 0.491 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.002 | 0.003 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.002 | 0.003 |
| Scholarly communication | 0.003 | 0.004 |
| Open science | 0.003 | 0.003 |
| Research integrity | 0.003 | 0.005 |
| Insufficient payload (model declined to judge) | 0.004 | 0.001 |
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; the direct Gemma label and the distilled Codex classifier agree on what is shown here.
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".