On the Statistical Optimality of Optimal Decision Trees

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Hauptverfasser: Xu, Zineng, Ghosh, Subhro, Tan, Yan Shuo
Format: Preprint
Veröffentlicht: 2026
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author Xu, Zineng
Ghosh, Subhro
Tan, Yan Shuo
author_facet Xu, Zineng
Ghosh, Subhro
Tan, Yan Shuo
contents While globally optimal empirical risk minimization (ERM) decision trees have become computationally feasible and empirically successful, rigorous theoretical guarantees for their statistical performance remain limited. In this work, we develop a comprehensive statistical theory for ERM trees under random design in both high-dimensional regression and classification. We first establish sharp oracle inequalities that bound the excess risk of the ERM estimator relative to the best possible approximation achievable by any tree with at most $L$ leaves, thereby characterizing the interpretability-accuracy trade-off. We derive these results using a novel uniform concentration framework based on empirically localized Rademacher complexity. Furthermore, we derive minimax optimal rates over a novel function class: the piecewise sparse heterogeneous anisotropic Besov (PSHAB) space. This space explicitly captures three key structural features encountered in practice: sparsity, anisotropic smoothness, and spatial heterogeneity. While our main results are established under sub-Gaussianity, we also provide robust guarantees that hold under heavy-tailed noise settings. Together, these findings provide a principled foundation for the optimality of ERM trees and introduce empirical process tools broadly applicable to other highly adaptive, data-driven procedures.
format Preprint
id arxiv_https___arxiv_org_abs_2603_05340
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle On the Statistical Optimality of Optimal Decision Trees
Xu, Zineng
Ghosh, Subhro
Tan, Yan Shuo
Machine Learning
Statistics Theory
62G08, 68Q32
While globally optimal empirical risk minimization (ERM) decision trees have become computationally feasible and empirically successful, rigorous theoretical guarantees for their statistical performance remain limited. In this work, we develop a comprehensive statistical theory for ERM trees under random design in both high-dimensional regression and classification. We first establish sharp oracle inequalities that bound the excess risk of the ERM estimator relative to the best possible approximation achievable by any tree with at most $L$ leaves, thereby characterizing the interpretability-accuracy trade-off. We derive these results using a novel uniform concentration framework based on empirically localized Rademacher complexity. Furthermore, we derive minimax optimal rates over a novel function class: the piecewise sparse heterogeneous anisotropic Besov (PSHAB) space. This space explicitly captures three key structural features encountered in practice: sparsity, anisotropic smoothness, and spatial heterogeneity. While our main results are established under sub-Gaussianity, we also provide robust guarantees that hold under heavy-tailed noise settings. Together, these findings provide a principled foundation for the optimality of ERM trees and introduce empirical process tools broadly applicable to other highly adaptive, data-driven procedures.
title On the Statistical Optimality of Optimal Decision Trees
topic Machine Learning
Statistics Theory
62G08, 68Q32
url https://arxiv.org/abs/2603.05340