Other Issues to Keep in Mind

This approach, however, raises issues of multiplicity (see Section 7.10). Accordingly, lower p-values may be required to be able to declare a result as statistically significant. This means that an adjustment to the sample-size estimation formula is appropriate, with the precise nature of the adjustment being related to the number of outcomes to be tested. This adjustment raises the magnitude of the estimated sample size (Machin and Campbell, 2005). 

It is useful to keep several other issues in mind when conducting sample-size estimations, including the following  

Before discussing safety assessment in clinical trials, an overview of clinical trials is presented. This is pertinent to the discussion of safety data in this chapter and also to the discussion of efficacy data collected in clinical trials that follows in Chapter 11. 

Pharmaceutical clinical trials are often categorized into various phases, with any given trial being identified as belonging to one of them. These categories include Phase I, Phase II, and Phase III, and this common nomenclature was employed in Chapter 1 since it is likely that you were already familiar with it. However, there are alternate systems of categorization that are arguably more informative. A traditional description of phases is as follows  

New Drug Development Design, Methodology, and Analysis. By J. Rick Turner Copyright 2007 John Wiley Sons, Inc. 

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