Nonparametric inference for ratios of densities via uniformly valid and powerful permutation tests

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Hauptverfasser: Bordino, Alberto, Berrett, Thomas B.
Format: Preprint
Veröffentlicht: 2025
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author Bordino, Alberto
Berrett, Thomas B.
author_facet Bordino, Alberto
Berrett, Thomas B.
contents We propose the density ratio permutation test, a hypothesis test that assesses whether the ratio between two densities is proportional to a known function based on independent samples from each distribution. The test uses an efficient Markov Chain Monte Carlo scheme to draw weighted permutations of the pooled data, yielding exchangeable samples and finite sample validity. For power, if the statistic is an integral probability metric, our procedure is consistent under mild assumptions on the defining function class; specializing to a reproducing kernel Hilbert space, we introduce the shifted maximum mean discrepancy and prove minimax optimality of our test when a normalized difference between the densities lies in a Sobolev ball. We extend to the case of an unknown density ratio by estimating it on an independent training sample and derive type~I error bounds in terms of the estimation error as well as power results. This allows adapting our method to conditional two sample testing, making it a versatile tool for assessing covariate-shift and related assumptions, which frequently arise in transfer learning and causal inference. Finally, we validate our theoretical findings through experiments on both simulated and real-world datasets.
format Preprint
id arxiv_https___arxiv_org_abs_2505_24529
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Nonparametric inference for ratios of densities via uniformly valid and powerful permutation tests
Bordino, Alberto
Berrett, Thomas B.
Methodology
Statistics Theory
62G09 62G10
We propose the density ratio permutation test, a hypothesis test that assesses whether the ratio between two densities is proportional to a known function based on independent samples from each distribution. The test uses an efficient Markov Chain Monte Carlo scheme to draw weighted permutations of the pooled data, yielding exchangeable samples and finite sample validity. For power, if the statistic is an integral probability metric, our procedure is consistent under mild assumptions on the defining function class; specializing to a reproducing kernel Hilbert space, we introduce the shifted maximum mean discrepancy and prove minimax optimality of our test when a normalized difference between the densities lies in a Sobolev ball. We extend to the case of an unknown density ratio by estimating it on an independent training sample and derive type~I error bounds in terms of the estimation error as well as power results. This allows adapting our method to conditional two sample testing, making it a versatile tool for assessing covariate-shift and related assumptions, which frequently arise in transfer learning and causal inference. Finally, we validate our theoretical findings through experiments on both simulated and real-world datasets.
title Nonparametric inference for ratios of densities via uniformly valid and powerful permutation tests
topic Methodology
Statistics Theory
62G09 62G10
url https://arxiv.org/abs/2505.24529