Post Hoc Power Analysis -- Another View

Joshua Fogel, M.A.

Disclosures

Pharmacotherapy. 2001;21(9) 

Introduction

Drs. Levine and Ensom[1] advocate that publication of clinical trials of nonsignificance should state a confidence interval rather than a post hoc power analysis. Their discussion is quite valid. The psychology discipline has advocated for power analysis in reporting of empiric studies.[2]

Psychologists have an illustrious history of rigorous statistical expertise. Unlike other journals, all psychological journals published by the American Psychological Association require reporting of exact statistic values (e.g., F, t) and significance levels. Reporting of effect sizes are also encouraged. This reporting allows others to fully critique the statistical methods of a study.

Interestingly enough, in 1999 a committee of the American Psychological Association convened to discuss this issue among a variety of other statistical issues. In their discussion on power analysis, they concluded, "Once the study is analyzed, confidence intervals replace calculated power in describing results."[3] This policy is required for all submissions to American Psychological Association journals. I hope that in the near future, other journals will advocate this policy as well.

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