Decoupling and randomization for double-indexed permutation statistics
Mingxuan Zou, Jingfan Xu, Peng Ding, Fang Han
TL;DR
The paper addresses concentration for double-indexed permutation statistics (DIPS) by decomposing $Q_w$ into a single-indexed component and a degenerate DIPS $Q_d$, and then developing new decoupling and randomization inequalities to bound MGFs. It yields a genuine combinatorial Hanson-Wright-type inequality and a combinatorial Bennett inequality, with dimension-free tails that depend on norms like $\|\mathbf{C}\|_{F}$, $\|\mathbf{C}\|_{op}$, and related Hadamard-structured terms. The framework is illustrated through nonparametric examples (Mann-Whitney–Wilcoxon, Daniels, Chatterjee, Friedman–Rafsky) and an application to causal inference via regression adjustment under complete randomization. Together, these results provide new tools for concentration in design-based inference and broaden the scope of permutation-statistic analysis in statistics and econometrics.
Abstract
This paper introduces a version of decoupling and randomization to establish concentration inequalities for double-indexed permutation statistics. The results yield, among other applications, a new combinatorial Hanson-Wright inequality and a new combinatorial Bennett inequality. Several illustrative examples from rank-based statistics, graph-based statistics, and causal inference are also provided.
