arXiv:2608.06206stat.MLcs.LG2026-08

提出局部化置信预测的有限样本保证,解决模型在特定数据上的校准问题。

Beyond Marginal Validity: Finite-Sample Guarantees for Localized Conformal Prediction

  • 基于局部化核方法,在固定评分下构建条件覆盖与长度误差的高概率界。
  • 理论揭示带宽偏差-方差权衡:带宽越小,局部精度越高,但需足够校准样本。
  • 适用于需要高精度局部预测的场景,如医疗诊断或金融风险评估。

分位数校准预测为任意黑箱预测器提供了有限样本、分布无关的边际覆盖性,但边际有效性可能掩盖严重的协变量特异性校准偏差;而精确的分布无关条件覆盖在有限样本下不可实现。随机局部化分位数预测(RLCP)通过在测试点附近校准来缓解这一差距,同时保持边际覆盖性。然而,现有理论缺乏对实际局部集合联合控制条件有效性与最优效率的有限样本保证。本文提供此类保证:对于任意固定评分,在条件评分累积分布函数满足Hölder正则性及标准密度和核假设下,证明了在实际局部邻域上一致成立的条件覆盖偏差与相对于最优集合长度误差的高概率界。这些界分解为O(h^β)的局部化偏差项和随校准样本量减小的校准项,清晰揭示了带宽选择的偏差-方差权衡以及何时RLCP能逼近最优。此外,我们分析了数据分割学习的评分:当评分目标为枢轴评分(如分位数校准回归中),统一局部保证可分解为固定评分校准误差与统一评分估计误差,表明更优的学习能提升局部保证精度。

原文摘要 · Abstract (English)

Conformal prediction endows arbitrary black-box predictors with finite-sample, distribution-free marginal coverage, yet marginal validity can hide severe covariate-specific miscalibration, while exact distribution-free conditional coverage is finite-sample unattainable. Randomly localized conformal prediction (RLCP) mitigates this gap by calibrating near the test point while preserving marginal coverage. Existing theory, however, lacks finite-sample guarantees for the realized localized set that jointly control conditional validity and oracle efficiency. We provide such guarantees. For any fixed score, under Hölder regularity of the conditional score CDF and standard density and kernel assumptions, we prove high-probability bounds, uniform over a realized localization neighbourhood, for the conditional-coverage gap and the length error relative to the oracle. The bounds decompose into an $O(h^β)$ localization bias and a calibration term decreasing with calibration size, clarifying the bandwidth bias-variance tradeoff and when RLCP tracks the oracle. We also analyze data-split learned scores: when the score targets a pivotal score, as in conformalized quantile regression, uniform local guarantees decompose into fixed-score calibration and uniform score-estimation errors, showing that improved learning sharpens localized guarantees.

置信预测机器学习统计推断

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