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September 29, 2025
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Episode 31, “The Not So Promising Zone Design”

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In this episode of "In the Interim…", Dr. Scott Berry examines the mathematical foundations and efficiency claims of the promising zone design for adaptive sample size in clinical trials.

Episode 31 of "In the Interim…" examines the “promising zone” adaptive design. Dr. Scott Berry discusses the neat mathematical trick and the appeal: interim looks can trigger sample size increases without requiring alpha adjustment.

However, relying on the mathematical tricks and the desire to not spend alpha leads to marginal benefits over fixed designs and inferiority to group sequential designs.

Scott challenges the fixation on alpha preservation, urging teams to simulate adaptations rigorously and evaluate and compare approaches.

For anyone designing pivotal trials, this episode delivers precise, factual critique of the promising zone and practical guidance for designing adaptive sample size confirmatory trials.

Tune in today to learn more: https://www.berryconsultants.com/resource/31-the-not-so-promising-zone-design

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