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Influence of Step-Width Manipulation on Running Biomechanics

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Stepped wedge designs could reduce the required sample size in cluster randomized trials.

Willem Woertman¹, Esther de Hoop, Mirjam Moerbeek

¹Department for Health Evidence, Radboud University Medical Centre, 133, PO Box 9101, 6500 HB Nijmegen, The Netherlands.

Journal of Clinical Epidemiology

|March 26, 2013

Summary

A new formula simplifies sample size calculations for cluster randomized stepped wedge trials. This design is significantly more efficient, requiring fewer participants than parallel group or ANCOVA designs.

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Area of Science:

Biostatistics
Clinical Trials Methodology

Background:

Cluster randomized trials (CRTs) increasingly utilize the stepped wedge design.
Limited guidance exists for the design and analysis of CRTs using this approach.
A simple sample size formula for stepped wedge designs is currently lacking.

Purpose of the Study:

To develop a sample size formula for cluster randomized stepped wedge designs.
To provide a practical tool for researchers planning stepped wedge trials.
To address the need for clear sample size estimation strategies.

Main Methods:

Derived a design effect (sample size correction factor) for stepped wedge designs.
Incorporated factors such as cluster size, intracluster correlation, number of steps, and measurement frequency.
Compared the sample size requirements against parallel group and ANCOVA designs.

Main Results:

The derived formula accounts for both clustering and the specific stepped wedge design.
The design effect is influenced by the number of steps, baseline measurements, and measurements between steps.
Stepped wedge designs demonstrated a substantially smaller required sample size compared to parallel group and ANCOVA designs.

Conclusions:

The stepped wedge design offers superior sample size efficiency for cluster randomized trials.
This design is a more resource-efficient alternative to parallel group and ANCOVA designs.
The developed formula aids in planning more efficient CRTs.