The Spectral Representations Of The Simple Hypothesis Testing Problem
Barış Nakiboğlu
TL;DR
The work develops a non-asymptotic, spectral theory for simple hypothesis testing with randomized detectors under σ-finite measures. Central to the approach is the primitive entropy spectrum ${h(\cdot|_{{q}}^{{w}})}$ and the LR quantiles, which yield the dual representation ${\beta(\epsilon|w^q)=\sup_{\gamma\ge0} h(\gamma|w^q)-\gamma\epsilon}$ and connect the Type II error volume to the convex analysis framework. A new Change of Measure Lemma enables exact relations between different measure pairs via tilting, broadening Neyman–Pearson results beyond probability measures. The paper then provides sharp, non-asymptotic approximations for ${\beta}$ in memoryless and tilted settings, using Berry–Esseen bounds and Gaussian Mills ratio controls, illustrating the practical power of the spectral representation for finite-length hypothesis testing and potential extensions to broader information-theoretic problems.
Abstract
The convex conjugate (i.e., the Legendre transform) of Type II error probability (volume) as a function of Type I error probability (volume) is determined for the hypothesis testing problem with randomized detectors. The derivation relies on properties of likelihood ratio quantiles and is general enough to extend to the case of $σ$-finite measures in all non-trivial cases. The convex conjugate of the Type II error volume, called the primitive entropy spectrum, is expressed as an integral of the complementary distribution function of the likelihood ratio using a standard spectral identity. The resulting dual characterization of the Type II error volume leads to state of the art bounds for the case of product measures via Berry--Esseen theorem through a brief analysis relying on properties of the Gaussian Mills ratio, both with and without tilting.
