#cohen-d

Calculate and interpret effect sizes for statistical significance. Common effect sizes: 1. Cohen's d for t-tests: (M1-M2)/pooled SD. Small=0.2, medium=0.5, large=0.8. 2. Eta squared (η²) for ANOVA: SS_effect/SS_total. Small=0.01, medium=0.06, large=0.14. 3. Pearson's r for correlations: Small=0.10, medium=0.30, large=0.50. 4. Odds ratio for logistic regression: interpret as multiplicative change in odds. Confidence intervals: always report 95% CI around effect size estimates. Practical significance: consider whether effect size is meaningful in real-world context, not just statistical significance. Meta-analysis reporting: use standardized effect sizes (Hedges' g for small samples). Tools: Effect Size Calculator, JASP, R effsize package. Remember: effect size independent of sample size, unlike p-values.