RT Journal Article SR Electronic T1 Post hoc power analysis: is it an informative and meaningful analysis? JF General Psychiatry JO Gen Psych FD BMJ Publishing Group Ltd SP e100069 DO 10.1136/gpsych-2019-100069 VO 32 IS 4 A1 Zhang, Yiran A1 Hedo, Rita A1 Rivera, Anna A1 Rull, Rudolph A1 Richardson, Sabrina A1 Tu, Xin M YR 2019 UL http://gpsych.bmj.com/content/32/4/e100069.abstract AB Power analysis is a key component for planning prospective studies such as clinical trials. However, some journals in biomedical and psychosocial sciences ask for power analysis for data already collected and analysed before accepting manuscripts for publication. In this report, post hoc power analysis for retrospective studies is examined and the informativeness of understanding the power for detecting significant effects of the results analysed, using the same data on which the power analysis is based, is scrutinised. Monte Carlo simulation is used to investigate the performance of posthoc power analysis.