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Sample size in the planning and interpretation of clinical trials
1Department of Medicine, McMaster University, Hamilton, Ontario, Canada.
Thrombosis and Haemostasis
|December 18, 1987
Abstract:
An understanding of sample size determination is important in both planning and interpreting the results of clinical trials. A Type II error occurs when it is concluded that there is no difference between treatment groups, when in truth there is a difference. Such a false negative conclusion results from too few patients in a trial. In this review the principles of estimating sample size before a trial is commenced and evaluating the results of a negative completed trial are reviewed. Clinically relevant examples are used to illustrate these concepts.