power-analysis-guide
Installation
SKILL.md
Power Analysis Guide
Calculate appropriate sample sizes for your study using power analysis, understand effect sizes, and avoid underpowered or wastefully overpowered designs.
Core Concepts
The Four Parameters of Power Analysis
Every power analysis involves four interrelated quantities. Fix any three to solve for the fourth:
| Parameter | Symbol | Definition | Typical Value |
|---|---|---|---|
| Effect size | d, r, f, etc. | Magnitude of the phenomenon you expect to detect | Varies by field |
| Significance level (alpha) | alpha | Probability of Type I error (false positive) | 0.05 |
| Statistical power (1 - beta) | 1 - beta | Probability of detecting a true effect | 0.80 or 0.90 |
| Sample size | N | Number of observations needed | Solve for this |