Sample size determination in step-up testing procedures for multiple comparisons with a control

Publication Type

Journal Article

Publication Date

11-2010

Abstract

Step-up procedures have been shown to be powerful testing methods in clinical trials for comparisons of several treatments with a control. In this paper, a determination of the optimal sample size for a step-up procedure that allows a pre-specified power level to be attained is discussed. Various definitions of power, such as all-pairs power, any-pair power, per-pair power and average power, in one- and two-sided tests are considered. An extensive numerical study confirms that square root allocation of sample size among treatments provides a better approximation of the optimal sample size relative to equal allocation. Based on square root allocation, tables are constructed, and users can conveniently obtain the approximate required sample size for the selected configurations of parameters and power. For clinical studies with difficulties in recruiting patients or when additional subjects lead to a significant increase in cost, a more precise computation of the required sample size is recommended. In such circumstances, our proposed procedure may be adopted to obtain the optimal sample size. It is also found that, contrary to conventional belief, the optimal allocation may considerably reduce the total sample size requirement in certain cases. The determination of the required sample sizes using both allocation rules are illustrated with two examples in clinical studies.

Keywords

multiple comparisons with a control, power function, step-up test, familywise error rate

Discipline

Econometrics | Health Economics

Research Areas

Econometrics

Publication

Statistics in Medicine

Volume

29

Issue

26

First Page

2743

Last Page

2756

ISSN

0277-6715

Identifier

10.1002/sim.4045

Publisher

Wiley

Additional URL

https://doi.org/10.1002/sim.4045

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