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Methods Inf Med 2007; 46(06): 655-661
DOI: 10.3414/ME0295
Original Article
Schattauer GmbH

Proposals for Sample Size Calculation Programs

H. Heinzl
1   Core Unit for Medical Statistics and Informatics, Medical University of Vienna, Vienna, Austria
,
A. Benner
2   Central Unit for Biostatistics, German Cancer Research Center, Heidelberg, Germany
,
C. Ittrich
2   Central Unit for Biostatistics, German Cancer Research Center, Heidelberg, Germany
,
M. Mittlböck
1   Core Unit for Medical Statistics and Informatics, Medical University of Vienna, Vienna, Austria
› Author Affiliations
Further Information

Publication History

Received: 28 December 2004

Accepted: 12 September 2006

Publication Date:
12 January 2018 (online)

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Summary

Objectives : Numerous sample size calculation programs are available nowadays. They include both commercial products as well as public domain and open source applications. We propose modifications for these programs in order to even better support statistical consultation during the planning stage of a two-armed clinical trial.

Methods : Directional two-sided tests are commonly used for two-armed clinical trials. This may lead to a non-negligible Type III error risk in a severely underpowered study. In the case of a reasonably sized study the question for the so-called auxiliary alternative may evolve.

Results : We propose that sample size calculation programs should be able to compute i) Type III errors and the so-called (q-values, ii) minimum sample sizes required to keep the (q-values below pre-specified levels, and iii) detectable effect sizes of the so-called auxiliary alternatives.

Conclusions : Proposals iand ii are intended to help prevent irresponsibly underpowered clinical trials, whereas the proposal iii is meant as additional assistance for the planning of reasonably sized clinical trials.

Keywords

Directional two-sided hypothesis test - Type III error - sample size calculation - irresponsibly underpowered study - auxiliary alternative hypothesis
 

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