power analysis
A statistical calculation determining the sample size needed in psychiatric research to detect meaningful treatment differences with adequate probability.
Full Definition
Power analysis is a statistical procedure used to determine the appropriate sample size for psychiatric research studies before data collection begins. It calculates the probability of detecting a true treatment effect of a specified magnitude, considering factors such as effect size, significance level (alpha), and desired statistical power (typically 80% or 90%). Adequate power analysis ensures studies are neither underpowered (risking false negative results) nor overpowered (wasting resources).
Usage
Usage note: Distinguish between prospective power analysis (for planning) and post-hoc power analysis (after study completion).
In Context
- "Power analysis indicated that 150 participants per group would provide 80% power to detect the expected effect size." — Sample size justification
- "The study was adequately powered based on preliminary data from the pilot trial." — Statistical considerations