提出多变量残差标准化方法,提升不确定性量化精度。
Multivariate Standardized Residuals for Conformal Prediction
- 用学习的局部协方差对残差进行白化处理,解耦输出相关性。
- 基于马氏距离的非一致性评分实现闭式计算,避免昂贵采样。
- 支持缺失值、部分信息更新及输出变换,适用场景更广。
虽然分割合取预测保证边际覆盖,但接近更强的条件覆盖对于可靠的不确定性量化至关重要。然而,在异方差设置下,朴素合取分数往往表现不佳。在单变量回归中,这通常通过使用估计的局部分数方差对非一致性分数进行归一化来解决。本文提出该归一化在多变量设置中的自然扩展,有效白化残差,解耦输出相关性并标准化局部方差。此外,我们推导出一个充分条件,刻画了广泛分布类中标准化残差实现渐近条件覆盖的性质。我们证明,使用由学习的局部协方差诱导的马氏距离作为非一致性分数,提供了一种闭式、计算高效的机制,以捕捉输出间的相关性和异方差性,避免了基于累积分布函数的先前方法所需的昂贵采样。该结构可拓展至多种实际应用场景,包括处理缺失输出值、在部分信息揭示后精炼合取集,以及为输出变换构造有效合取集。最后,我们在合成与真实世界数据集上提供了广泛的实证证据,表明本方法生成的合取集在条件覆盖性能上优于现有主流多变量基线。
原文摘要 · Abstract (English)
While split conformal prediction guarantees marginal coverage, approaching the stronger property of conditional coverage is essential for reliable uncertainty quantification. Naive conformal scores, however, suffer from poor conditional coverage in heteroskedastic settings. In univariate regression, this is commonly addressed by normalizing non-conformity scores using an estimated local score variance. In this work, we propose a natural extension of this normalization to the multivariate setting, effectively whitening the residuals to decouple output correlations and standardize local variance. Furthermore, we derive a sufficient condition characterizing a broad class of distributions for which standardized residuals yield asymptotic conditional coverage. We demonstrate that using the Mahalanobis distance induced by a learned local covariance as a non-conformity score provides a closed-form, computationally efficient mechanism for capturing inter-output correlations and heteroskedasticity, avoiding the expensive sampling required by previous methods based on cumulative distribution functions. This structure unlocks several practical extensions, including the handling of missing output values, the refinement of conformal sets when partial information is revealed, and the construction of valid conformal sets for transformations of the output. Finally, we provide extensive empirical evidence on both synthetic and real-world datasets showing that our approach yields conformal sets that improve upon the conditional coverage of existing multivariate baselines.
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