Block 97: Effect Sizes & Practical Significance
Move beyond p-values to measure the magnitude of effects.
Concepts
- Cohen's d for mean differences
- Correlation r as effect size
- Practical vs statistical significance
- Sample size and statistical power
Code Examples
See exercise below.
Exercise
Compute Cohen's d for a two-group comparison. Interpret: small/medium/large effect. Compare two scenarios: large sample, small effect vs small sample, large effect. Discuss which is more meaningful.
Homework
Why can a tiny p-value accompany a practically unimportant effect? Illustrate with numbers.