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Summary

This study introduces a new power function for stepped-wedge (SW) trials, accounting for complex three-level data structures. This improves sample size calculations for stepped-wedge (SW) study designs.

Keywords:
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Area of Science:

  • Biostatistics
  • Clinical Trial Design
  • Epidemiology

Background:

  • Stepped-wedge (SW) designs are increasingly used in clinical research.
  • SW designs often involve three-level hierarchical data (participants within periods within clusters).
  • Existing power calculations do not adequately address the complexities of three-level SW data, specifically second-level correlations.

Purpose of the Study:

  • To derive an explicit power function for three-level continuous outcome data in SW trials.
  • To incorporate both first and second-level correlations into power analysis for SW designs.
  • To evaluate the performance of the new power function and compare it with existing methods.

Main Methods:

  • Derived a closed-form power function based on a statistical model for three-level continuous outcome data.
  • Utilized a fixed-effect meta-analytic approach to derive the sampling distribution of a pooled intervention effect estimate.
  • Conducted simulation studies to verify the power function's accuracy and applicability across different data structures.

Main Results:

  • The derived power function is unbiased and performs well with varying numbers of participants per period per cluster.
  • When applied to two-level data structures, a power function based on a marginal estimate outperformed one based on a pooled estimate.
  • The study suggests extensions for power functions applicable to binary outcomes in SW trials.

Conclusions:

  • The developed power function provides a more accurate method for sample size determination in three-level SW trials.
  • Accounting for hierarchical correlations is crucial for robust power calculations in complex trial designs.
  • Further research is recommended for extending these methods to binary outcomes and other complex SW trial variations.