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Summary

This study introduces local alternatives for sample size re-estimation (SSR) in blinded experiments, showing consistent parameter estimates and optimal sample sizes. This approach validates SSR for hypothesis testing with clinically relevant effect sizes.

Keywords:
adaptive designasymptotic distribution theoryblinded datalocal alternativesmaximum likelihood estimation

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Area of Science:

  • Biostatistics
  • Clinical Trials Methodology
  • Statistical Inference

Background:

  • Existing literature on maximum likelihood estimators under fixed alternatives shows inconsistent nuisance parameter estimates with sample size re-estimation (SSR) in blinded studies.
  • These findings have limited the application of SSR in clinical trial design.
  • The use of fixed alternatives leads to unrealistic power convergence and hinders robust statistical analysis.

Purpose of the Study:

  • To propose the use of local alternatives instead of fixed alternatives for analyzing blinded experiments.
  • To demonstrate the consistency of nuisance parameter estimates and the convergence of sample sizes to optimal values under local alternatives.
  • To validate the practical utility of SSR procedures in hypothesis testing with predetermined effect sizes.

Main Methods:

  • Treatment assignments in blinded experiments are treated as missing data, imputed using single imputation from marginal distributions.
  • The first step of the Expectation-Maximization (EM) algorithm is employed, mimicking imputation under the null hypothesis.
  • Monte-Carlo simulation studies are used to confirm theoretical findings, alongside a multiple logistic regression example for practical illustration.

Main Results:

  • Under local alternatives, both blinded and unblinded estimates of nuisance parameters are shown to be consistent.
  • Re-estimated sample sizes converge to their locally asymptotically optimal values.
  • Simulation studies confirm the theoretical findings, demonstrating the robustness of the proposed method.

Conclusions:

  • The study advocates for the use of local alternatives in hypothesis testing for blinded experiments.
  • Both blinded and unblinded SSR procedures yield similar sample sizes and power when a minimally clinically relevant local effect size is predetermined.
  • The findings support the practical application of SSR, enhancing the efficiency and reliability of clinical trial designs.