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A complete characterization of sequential testability and change detectability in i.i.d. models

arXiv · AI, language, vision and robotics · article · Sep 4, 2026 · UTC

We give a necessary and sufficient condition for the existence of power-one sequential tests in an i.i.d. composite testing problem. A level-\(α\) test with power one against every alternative exists if and only if the alternatives are separated from the null by a countable family of finite-block events. We provide other equivalent conditions using randomized fixed-sample tests, bounded finite-block scores, e-processes, reduced-filtration test supermartingales, and a countable cover whose finite-block weak-$*$ closed convex hulls are positively separated in total variation. As a bonus, the con

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First collected: 2026-09-20T21:52:07.471Z. This is not the publication date.