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To the Editor: Mr Halpern and colleagues¹ argue that underpowered clinical trials are ethically justified only in 2 situations: (1) interventions for rare diseases in which investigators document explicit plans for including their results with those of similar trials in a prospective meta-analyses and (2) early-phase trials in the development of drugs or devices provided that they are adequately powered for defined purposes other than randomized treatment comparison.

I believe that the concept of statistical power as an absolute is misleading. Statistical power is typically presented as a dichotomy that defines a cutoff of .80 or greater. In fact, the concept of statistical power exists along a continuum. A value for statistical power is intrinsically related to the level of statistical significance, the level of treatment differences, variability of response, research question of interest, and sample size. Separating statistical power from these other parameters misinterprets the issue of statistical power. . . . [Full Text of this Article]

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