Pearson's r and r²: direction, strength, outliers and causality

What this note covers

1. What Pearson's correlation coefficient actually measures
2. Getting r and r² out of your calculator reliably
3. Interpreting r: strength and direction in words
4. The coefficient of determination r² and what it means in context
5. Outliers: identifying them, their effect on r, and when removal is justified
6. Correlation is not causation
7. Worked example: r, r², an outlier and a causal claim
8. How this is examined in the SACE paper — and what separates a top answer

8 sections · 12 key terms & formulas · 6 common mistakes