Statistical Power
Definition
\(\text{Power} = 1 - \beta\)
= probability of rejecting \(H_0\) when it is false
Interpretation
- High power = test is good at detecting a true difference
- Low power = high chance of missing a true difference
What affects power?
- Sample size (n↑ → power↑)
- Significance level (\(\alpha\)↑ → power↑)
- True effect size (larger difference → power↑)
- Population variance (lower variance → power↑)
Convention
Desired power: at least 80% (0.8)