AP Statistics / Unit 5: Regression Analysis
5.2 Correlation
Notes
The correlation $r$ measures the direction and strength of a linear relationship.
- $-1\le r\le1$; no units; unchanged by unit conversions.
- Not resistant to outliers. Correlation isn't causation.
Practice
$r=-0.92$ means:
Close to $-1$.
Converting heights from inches to cm changes $r$:
$r$ has no units.
A strong curved relationship can have $r$ near:
$r$ only measures linear strength.
Ready for more? Take the Unit 5 test.