Misplaced Confidence in Observed Power

Abstract

A recently published randomized controlled trial in JAMA investigated the impact of the selective serotonin reuptake inhibitor, escitalopram, on the risk of major adverse events (MACE). The authors estimated a hazard ratio (HR) of 0.69 (95% CI: 0.49, 0.96; $p$ = 0.03) and then attempted to calculate how much statistical power their study (test) had attained, and used this measure to assess how reliable their results were. Here, we discuss why this approach, along with other post-hoc power analyses, are highly misleading.