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Minimising errors in clinical studies by proper selection of sample size.
1Department of Epidemiology and Population Science, London School of Hygiene and Tropical Medicine.
Annals of the Academy of Medicine, Singapore
|January 1, 1991
Summary
Calculating the appropriate sample size is crucial for clinical trial planning. This involves understanding statistical concepts like Type I and Type II errors to ensure trials are neither trivial nor wasteful.
Area of Science:
- Biostatistics
- Clinical Trial Design
- Statistical Power Analysis
Background:
- Clinical trial planning necessitates careful consideration of statistical principles.
- Understanding concepts like Type I and Type II errors, significance, and power is fundamental.
Purpose of the Study:
- To provide guidance on calculating sample size for clinical trials.
- To explain the statistical underpinnings of sample size determination.
- To offer practical tools and examples for sample size calculation.
Main Methods:
- Explanation of statistical terms: Type I and Type II errors, significance, and power.
- Presentation of formulae for sample size calculation in parallel group and matched pair/cross-over designs.
- Inclusion of sample size tables and worked examples for practical application.
Main Results:
- Sample size is determined by significance level, power, and the effect size to be detected.
- Estimation of standard deviation often relies on limited preliminary data.
- Precise sample size determination is not feasible; a sensible range exists.
Conclusions:
- The optimal sample size balances statistical validity with ethical and resource considerations.
- Clinical trials should be adequately powered without being unnecessarily large.
- Effective sample size planning prevents trivial results and resource wastage.