Recognition: unknown
Betting on Bets: Anytime-Valid Tests for Stochastic Dominance
Pith reviewed 2026-05-09 20:53 UTC · model grok-4.3
The pith
Sequential tests for stochastic dominance achieve power one by mixing asymptotically growth-rate optimal e-variables.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
We develop a novel family of sequential, anytime-valid tests for stochastic dominance by constructing e-processes as mixtures of asymptotically growth-rate optimal e-variables. These yield power-one tests that remain valid under continuous monitoring. The construction is nonparametric for first-order stochastic dominance and extends directly to any higher-order version.
What carries the argument
Mixture of asymptotically growth-rate optimal e-variables forming an e-process that quantifies accumulating evidence against the null of no stochastic dominance.
If this is right
- The tests achieve power one, eventually rejecting the null almost surely when dominance holds.
- Validity is preserved for any stopping time or continuous monitoring schedule.
- The same mixing construction applies to higher-order stochastic dominance.
- Empirical power matches or approaches that of standard non-sequential tests for fixed samples.
Where Pith is reading between the lines
- The framework could support ongoing monitoring of investment or treatment prospects without pre-fixing sample sizes.
- Conditions sketched for testing the complementary non-dominance null might enable detection of definite upside in sequential settings.
- Similar mixtures could be explored for related ordering concepts such as convex stochastic order.
Load-bearing premise
Mixtures of asymptotically growth-rate optimal e-variables for the stochastic dominance null will produce processes that grow without bound under the alternative while staying valid at all times.
What would settle it
A data-generating process where one distribution truly dominates the other yet the constructed evidence process remains bounded, or where the test rejects the null too often when monitoring continuously on identical distributions.
Figures
read the original abstract
How can we monitor, in real time, whether one uncertain prospect has any upside over another? To answer this question, we develop a novel family of sequential, anytime-valid tests for stochastic dominance (SD; also known as stochastic ordering), a classical and popular notion for comparing entire distribution functions. The problem is distinct from the popular problem of testing for dominance in means, which would not capture distributional differences beyond the first moment. We first derive powerful, nonparametric e-processes that quantify evidence against the null hypothesis that one prospect is dominated by another. For first-order SD, these e-processes are constructed as a mixture of asymptotically growth-rate optimal e-variables and yield a test of power one. The approach further generalizes to sequential testing for SD beyond the first order, including any higher-order SD. Empirically, we demonstrate that the resulting sequential tests are competitive with existing non-sequential SD tests in terms of power, while achieving validity under continuous monitoring that existing methods do not. Finally, we sketch the complementary and challenging problem of testing the non-SD null hypothesis, which asks whether a prospect has a definite upside, and describe the conditions under which we can derive a nontrivial anytime-valid test.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper develops a family of sequential, anytime-valid tests for stochastic dominance (SD) using nonparametric e-processes. For first-order SD, the e-processes are constructed as mixtures of asymptotically growth-rate optimal e-variables and are claimed to yield power-one tests under the alternative while remaining valid under continuous monitoring. The approach generalizes to higher-order SD, and the manuscript includes empirical comparisons showing competitiveness with non-sequential SD tests plus a sketch of the complementary problem of testing the non-SD null.
Significance. If the derivations and power-one claims hold, the work supplies a practical tool for real-time monitoring of distributional dominance that existing fixed-sample tests lack. The grounding in e-process theory for a composite nonparametric null is a clear strength, as is the explicit generalization beyond first-order SD and the empirical demonstration of power competitiveness. These features address a genuine gap in sequential nonparametric testing with direct relevance to economics and decision theory.
major comments (2)
- [§3.2] §3.2, the mixture construction: the claim that the e-process is a mixture of asymptotically growth-rate optimal e-variables for the first-order SD null requires an explicit statement of the mixing measure and a proof that the resulting process retains the growth-rate optimality (or at least the power-one property) under the alternative; without this, the power-one guarantee cannot be verified from the given construction.
- [§4] §4, generalization to higher-order SD: the extension from first-order to k-th order SD is sketched but the corresponding e-variable family and the validity argument under continuous monitoring are not derived in detail; this is load-bearing for the claim that the method 'further generalizes' and needs at least a theorem statement with the key steps.
minor comments (2)
- [Throughout] Notation for the e-processes (e.g., the distinction between the instantaneous e-variable and the cumulative process) is introduced without a consolidated table or definition list, making it easy to lose track across sections.
- [§5] The empirical section would benefit from reporting the exact sample sizes and number of Monte Carlo replications used to generate the power curves, as well as a direct comparison of type-I error under continuous monitoring versus fixed-sample benchmarks.
Simulated Author's Rebuttal
We thank the referee for the positive evaluation and the recommendation for minor revision. We address the two major comments point by point below, agreeing that greater explicitness is needed in both cases. The requested clarifications will be incorporated into the revised manuscript.
read point-by-point responses
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Referee: [§3.2] §3.2, the mixture construction: the claim that the e-process is a mixture of asymptotically growth-rate optimal e-variables for the first-order SD null requires an explicit statement of the mixing measure and a proof that the resulting process retains the growth-rate optimality (or at least the power-one property) under the alternative; without this, the power-one guarantee cannot be verified from the given construction.
Authors: We agree that an explicit statement of the mixing measure and a supporting argument for the power-one property are required for full verifiability. In the revision we will state the mixing measure precisely (a probability measure supported on the class of asymptotically growth-rate optimal e-variables for the first-order SD null) and add a short lemma establishing that the resulting mixture e-process inherits the power-one property under the alternative. This addition will be placed in §3.2 immediately after the construction. revision: yes
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Referee: [§4] §4, generalization to higher-order SD: the extension from first-order to k-th order SD is sketched but the corresponding e-variable family and the validity argument under continuous monitoring are not derived in detail; this is load-bearing for the claim that the method 'further generalizes' and needs at least a theorem statement with the key steps.
Authors: We acknowledge that the higher-order extension is currently only sketched. We will expand §4 with a formal theorem that (i) defines the family of e-variables for k-th order SD, (ii) states the corresponding e-process, and (iii) outlines the key steps establishing anytime-validity under continuous monitoring. The proof will adapt the first-order argument via the appropriate integral representation of higher-order dominance. revision: yes
Circularity Check
No significant circularity in derivation chain
full rationale
The paper constructs e-processes for stochastic dominance testing by mixing asymptotically growth-rate optimal e-variables drawn from established sequential testing theory. This step relies on external optimality results for e-variables under composite nonparametric nulls rather than defining the target quantity in terms of itself or fitting parameters to the same data used for validation. No load-bearing self-citations reduce the central claim to unverified prior work by the same authors; the power-one property and continuous-monitoring validity follow directly from the mixture construction and standard e-process martingale properties. The derivation remains self-contained against external benchmarks in e-process literature.
Axiom & Free-Parameter Ledger
Reference graph
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