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Methods for specifying the target difference in a randomised controlled trial: the Difference ELicitation in TriAls
Jenni Hislop1, Temitope E Adewuyi2, Luke D Vale1
1Institute of Health and Society, Newcastle University, Newcastle upon Tyne, United Kingdom.
Plos Medicine
|May 15, 2014
Summary
Researchers can choose from seven methods to determine the target difference for sample size calculations in randomised controlled trials (RCTs). The best method depends on the study
Area of Science:
- Clinical Trials Methodology
- Biostatistics
- Health Services Research
Background:
- Randomised controlled trials (RCTs) are the gold standard for evaluating healthcare interventions.
- Sample size calculations in RCTs require specifying a target difference to ensure statistical power.
- Inadequate specification of the target difference can lead to underpowered or over-powered studies.
Purpose of the Study:
- To systematically review and identify methods for specifying the target difference in RCT sample size calculations.
- To provide guidance on selecting appropriate methods based on study aims and context.
Main Methods:
- Comprehensive systematic review of medical and non-medical literature.
- Searched multiple databases (MEDLINE, EMBASE, Cochrane Library, etc.) from 1966 to 2011.
- Included 777 studies and 15 textbooks, synthesizing findings through narrative synthesis.
Main Results:
- Identified seven distinct methods for specifying the target difference:
- Anchor, distribution, health economic, opinion-seeking, pilot study, review of the evidence base, and standardized effect size.
- Methods vary in their suitability for defining important versus realistic differences.
Conclusions:
- Multiple methods exist for specifying the target difference in RCT sample size calculations.
- The choice of method depends on the study's aim, context, and statistical framework.
- No single method is universally optimal; guidance is provided for selection.
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