arXiv Machine Learning

Performance metrics in machine learning: a scenario-based guide from the confusion matrix to calibration, regression and uncertainty

arXiv AI
Oct 28

When uncertainty quantification fails: structural vulnerabilities and corrections for selective prediction under clinical class imbalance

The paper investigates how uncertainty quantification fails in selective prediction systems when clinical data exhibit severe class imbalance, leading to systematic exclusion of minority patients. Through experiments on 56 synthetic scenarios and three neurodegenerative disease cohorts, the authors show that standard uncertainty measures become proxies for class membership rather than true ambiguity, and that combining class‑aware correction (CCR) with threshold‑aware metrics restores proper monotonicity and protects minority patients. The study proposes adopting threshold‑aligned uncertainty measures and class‑stratified evaluation to mitigate this bias and improve safety in clinical AI pipelines.

By Walter Endrizzi, Flavio Ragni, Raffaele Marchesi, Stefano Bovo, Monica Moroni, Giuseppe Jurman, Venet Osmani
arXiv Statistics ML
Aug 24

EDGE: a closed-form directed test for the calibration of probabilistic binary classifiers

The paper introduces EDGE, a closed‑form statistical test for assessing the calibration of probabilistic binary classifiers, specifically logistic regression. EDGE uses the same binned predicted‑versus‑observed table as a reliability diagram, projects standardized bin residuals onto a small basis of smooth calibration‑distortion shapes, and yields a null distribution that is a weighted sum of chi‑square variables. The method requires only a single pass over the data and a small eigendecomposition, avoiding refitting, resampling, or tuning, and remains robust in sparse or misspecified settings where other binned tests fail.

By Ebrahim Khaled Ebrahim, Ahmed El-Kotory
arXiv AI
Sep 2

Counterfactual Fragility Certificates: Exposing High-Confidence Brittleness under Structured Evidence Failure

The paper introduces Counterfactual Fragility Certificates (CFC), a model‑agnostic audit protocol that maps each prediction to an evidence‑failure trajectory, summarizing it with metrics such as greedy flip budget, margin‑collapse area, degradation thresholds, and fragility dominance score. CFC is shown to identify brittle high‑confidence predictions on seven tabular benchmarks with an AUROC of 0.915, outperforming existing scalar scores by up to +0.405. The method remains effective across various perturbation and review‑budget scenarios, and can also inform fragility‑aware regularization and temperature correction.

By Filippo Cenacchi, Longbing Cao, Runze Yang
arXiv Computer Vision
Sep 17

Beyond Performance Metrics: Uncertainty Mapping of Label Ambiguity in Fazekas Score Prediction

The paper introduces an uncertainty‑mapping framework for periventricular Fazekas score prediction, moving beyond standard performance metrics. By linking uncertainty to positions in the learned feature space, it identifies class‑boundary regions where predictions are ambiguous and highlights potential label disagreements. The study shows that different loss functions affect the uncertainty profile, with some models achieving clearer class separation and more localized uncertainty.

By Susanne Schmid, Johanna Ospel, Richard Frayne, Roberto Souza
arXiv Computation and Language
Aug 24

An ambiguity taxonomy for evaluating large language model performance on clinical registry abstraction: a multi-site prospective study

The study evaluates large language models (LLMs) on unprocessed electronic medical record data for clinical registry abstraction, focusing on the American College of Cardiology National Cardiovascular Data Registry. In a pilot at one academic center, the LLM identified candidate data sources for each registry question, which abstractors used to define question‑specific document sets. In a subsequent validation at a second center, the LLM answered 157 registry questions with an overall mean accuracy of 91.5%, but accuracy dropped from 96% for simple medication or event flag questions to 62% for event timing questions, reflecting increasing ambiguity and required clinical reasoning.

By James Matheson, Betsy Castillo, Andrew Y. Shin, David Scheinker
arXiv AI
Sep 1

Benchmark Contamination: A Taxonomy Organized by Defeated Mitigation

The paper introduces a new taxonomy for benchmark contamination that categorizes leakage by the mitigation it defeats—direct, derivative, temporal, distributional, and acquired—covering both training‑time and evaluation‑time scenarios. It proposes a four‑field disclosure protocol to record contamination status alongside benchmark scores, and provides a JSON schema, validator, and examples. An empirical study of 41 documents using a pre‑registered instrument shows limited reporting of contamination types and variable reliability, highlighting gaps in current disclosure practices.

By Johanna Angulo, V\'ictor Yeste, Hector Espinos-Morato