Skip to main content

Sample size calculations and specifying the target difference for randomized trials

An article collection published in Trials.

Edited by Dr. Suzie Cro

A key step in the design of a randomized controlled trial (RCT) is the estimation of the number of participants needed. Despite the critical role of the target difference in the primary outcome in a conventional RCT sample size, the manner in which it is determined, has received relatively little attention. Additionally, guidance on the reporting of the sample size calculation for a RCT is sorely needed. This article collection addresses these gaps in the literature. It includes a summary of the new DELTA2 guidance for researchers and funder representatives on the specification and reporting of the target difference and the sample size calculation for an RCT. Further articles address how the DELTA2 guidance was developed, previous guidance on this topic, along with a review of practice in a cohort of RCTs and a commentary on the value of the new guidance.

  1. A key step in the design of a RCT is the estimation of the number of participants needed in the study. The most common approach is to specify a target difference between the treatments for the primary outcome ...

    Authors: Jonathan A. Cook, Steven A. Julious, William Sones, Lisa V. Hampson, Catherine Hewitt, Jesse A. Berlin, Deborah Ashby, Richard Emsley, Dean A. Fergusson, Stephen J. Walters, Edward C. F. Wilson, Graeme Maclennan, Nigel Stallard, Joanne C. Rothwell, Martin Bland, Louise Brown…
    Citation: Trials 2018 19:606
    Content type: Methodology Published on:

  3. When designing a randomised controlled trial (RCT), an important consideration is the sample size required. This is calculated from several components; one of which is the target difference. This study aims to...

    Authors: Joanne C. Rothwell, Steven A. Julious and Cindy L. Cooper
    Citation: Trials 2018 19:544
    Content type: Research Published on:

  4. A key step in the design of a randomised controlled trial is the estimation of the number of participants needed. The most common approach is to specify a target difference in the primary outcome between the r...

    Authors: William Sones, Steven A. Julious, Joanne C. Rothwell, Craig Robert Ramsay, Lisa V. Hampson, Richard Emsley, Stephen J. Walters, Catherine Hewitt, Martin Bland, Dean A. Fergusson, Jesse A. Berlin, Doug Altman, Luke David Vale and Jonathan Alistair Cook
    Citation: Trials 2018 19:542
    Content type: Research Published on:

    The Correction to this article has been published in Trials 2019 20:602

  5. A key step in the design of a randomised controlled trial (RCT) is the estimation of the number of participants needed. By far the most common approach is to specify a target difference and then estimate the c...

    Authors: Jonathan A. Cook, Steven A. Julious, William Sones, Joanne C. Rothwell, Craig R. Ramsay, Lisa V. Hampson, Richard Emsley, Stephen J. Walters, Catherine Hewitt, Martin Bland, Dean A. Fergusson, Jesse A. Berlin, Doug Altman and Luke D. Vale
    Citation: Trials 2017 18:271
    Content type: Study protocol Published on:

  6. Central to the design of a randomised controlled trial is the calculation of the number of participants needed. This is typically achieved by specifying a target difference and calculating the corresponding sa...

    Authors: Jonathan A Cook, Jenni Hislop, Douglas G Altman, Peter Fayers, Andrew H Briggs, Craig R Ramsay, John D Norrie, Ian M Harvey, Brian Buckley, Dean Fergusson, Ian Ford and Luke D Vale
    Citation: Trials 2015 16:12
    Content type: Research Published on: