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Exact group sequential designs for two-arm experiments with Poisson distributed outcome variables

Lookup NU author(s): Dr Michael GraylingORCiD, Professor James WasonORCiD



This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


© 2019, Published by Taylor & Francis Group, LLC. © 2019, © Michael J. Grayling, James M. S. Wason, and Adrian P. Mander. We describe and compare two methods for the group sequential design of two-arm experiments with Poisson distributed data, which are based on a normal approximation and exact calculations respectively. A framework to determine near-optimal stopping boundaries is also presented. Using this framework, for a considered example, we demonstrate that a group sequential design could reduce the expected sample size under the null hypothesis by as much as 44% compared to a fixed sample approach. We conclude with a discussion of the advantages and disadvantages of the two presented procedures.

Publication metadata

Author(s): Grayling MJ, Wason JMS, Mander AP

Publication type: Article

Publication status: Published

Journal: Communications in Statistics - Theory and Methods

Year: 2021

Volume: 50

Issue: 1

Pages: 18-34

Online publication date: 17/06/2019

Acceptance date: 31/05/2019

Date deposited: 08/07/2019

ISSN (print): 0361-0926

ISSN (electronic): 1532-415X

Publisher: Taylor and Francis Inc.


DOI: 10.1080/03610926.2019.1628273


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