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Schizophrenia Bulletin Advance Access published online on May 9, 2008
Schizophrenia Bulletin, doi:10.1093/schbul/sbn035
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© The Author 2008. Published by Oxford University Press on behalf of the Maryland Psychiatric Research Center. All rights reserved. For permissions, please email: journals.permissions@oxfordjournals.org.

Implications of Clinical Trial Design on Sample Size Requirements

Andrew C. Leon1,2
2 Weill Medical College of Cornell University, New York, NY

1 To whom correspondence should be addressed; Department of Psychiatry, Weill Medical College of Cornell University, Box 140, 525 East 68th Street, New York, NY 10065; tel: 212-746-3872, fax: 212-746-8754, e-mail: acleon{at}med.cornell.edu.

The primary goal in designing a randomized controlled clinical trial (RCT) is to minimize bias in the estimate of treatment effect. Randomized group assignment, double-blinded assessments, and control or comparison groups reduce the risk of bias. The design must also provide sufficient statistical power to detect a clinically meaningful treatment effect and maintain a nominal level of type I error. An attempt to integrate neurocognitive science into an RCT poses additional challenges. Two particularly relevant aspects of such a design often receive insufficient attention in an RCT. Multiple outcomes inflate type I error, and an unreliable assessment process introduces bias and reduces statistical power. Here we describe how both unreliability and multiple outcomes can increase the study costs and duration and reduce the feasibility of the study. The objective of this article is to consider strategies that overcome the problems of unreliability and multiplicity.

Keywords: multiplicity / reliability / sample size / statistical power


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