{
  "abstract": "Complete stepped-wedge designs guarantee eventual intervention delivery, but their final periods contain no concurrent controls. Under exposure-time heterogeneity this creates a design-analysis tension: a constant-effect analysis can be precise while targeting a design-dependent contrast, whereas an exposure-time indicator (ETI) analysis targets a prespecified time-averaged effect but may be much less precise. We develop an adequacy radius that quantifies the size of exposure-time heterogeneity compatible with a prespecified tolerance for estimand mismatch, and combine it with precision calculations to compare complete wedges with rollout-constrained hybrid designs that retain a wait-list arm. For a balanced wedge with a wait-list under the Hussey-Hughes model, the wait-list share and the correlation act on the constant-effect GLS estimand through a single scalar; we prove that the radius increases strictly with the wait-list share and decreases strictly with the within-cluster correlation, but remains bounded. Numerical optimisation and a model-based redesign of a weekend allied-health trial show that intermediate hybrids make estimand-aligned ETI analysis materially more affordable, giving a robustness-precision frontier rather than a binary choice between a complete wedge and a parallel trial. A second trial, of digital adherence support for tuberculosis treatment, has the same radius but no detectable heterogeneity; its test of a constant effect would detect heterogeneity large enough to halve the coverage of the nominal interval only 37% of the time. The contribution is a diagnostic and design principle: when exposure-time heterogeneity is plausible, retaining concurrent controls reduces the price of analysing the estimand one intends to report.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.35853",
  "author_total": 2,
  "authors": [
    {
      "name": "Stanisław M. S. Halkiewicz"
    },
    {
      "name": "Sergey Alexeev"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/a55y6c4b5vbgy.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.35853",
  "fulltext_url": null,
  "id": "a55y6c4b5vbgy",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.35853",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "econ.EM"
    ],
    [
      "arxiv",
      "stat.AP"
    ],
    [
      "arxiv",
      "stat.ME"
    ],
    [
      "openalex",
      "2613|Statistical Methods in Clinical Trials"
    ]
  ],
  "openalex": "W7223864744",
  "pdf_url": "https://arxiv.org/pdf/2610.35853",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-26",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/a55y6c4b5vbgy.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:35:49Z",
      "native_id": "2610.35853",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.35853"
    }
  ],
  "subjects": [
    {
      "field": "mathematics",
      "origin": "arxiv:stat.AP",
      "subfield": "statistics"
    }
  ],
  "title": "Adequacy radii for stepped-wedge trials with time-varying effects",
  "title_text": "Adequacy radii for stepped-wedge trials with time-varying effects",
  "type": "preprint",
  "updated_at": "2026-10-30T12:35:49Z",
  "url": "https://research.draconitic.com/paper/a55y6c4b5vbgy",
  "venue": "arXiv",
  "versions": []
}