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A Note on the Sample Size Formula for a Win Ratio Endpoint.

Se Yoon Lee1

  • 1Department of Statistics, Texas A&M University, College Station, Texas, USA.

Statistics in Medicine
|July 15, 2025
PubMed
Summary
This summary is machine-generated.

The Yu and Ganju sample size formula for win ratio endpoints may underestimate statistical power. Using approximated null variance instead of exact permutation variance can lead to lower power in clinical trial analysis.

Keywords:
overestimation of variancesample size formulawin ratio endpoint

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Area of Science:

  • Biostatistics
  • Clinical Trial Design
  • Statistical Power Analysis

Background:

  • The win ratio is a composite endpoint increasingly used in clinical trials.
  • The Yu and Ganju (YG) formula offers a simplified approach to sample size calculation for win ratio endpoints.
  • This formula utilizes an approximated null variance, differing from the original Finkelstein and Schoenfeld (FS) exact permutation variance.

Discussion:

  • This study re-evaluates the YG sample size formula from an implementation standpoint.
  • Empirical analysis reveals that the YG formula's power is generally lower than that derived from the FS exact permutation variance.
  • The discrepancy is attributed to the overestimation of true variance when using approximated null variance.

Key Insights:

  • The YG formula's reliance on approximated null variance can lead to underestimation of statistical power.
  • Practitioners may face challenges in achieving desired power due to this discrepancy.
  • Accurate sample size determination is crucial for the validity of clinical trial results.

Outlook:

  • Further research is needed to refine sample size methodologies for win ratio endpoints.
  • Encouraging discussion on the appropriate application and limitations of the YG formula is essential.
  • Consideration of exact permutation variance may be necessary for robust power calculations.