Math
Correlation.
Definition
Correlation measures the strength and direction of the linear relationship between two quantitative variables. The correlation coefficient r ranges from -1 to 1, where values near ±1 indicate strong linear relationships and values near 0 indicate weak or no linear relationship.
Examples
Real-world.
- 1 Height and weight typically have a positive correlation (r ≈ 0.7)
- 2 Hours of TV watched and GPA might have a negative correlation
- 3 Shoe size and intelligence have roughly zero correlation
Key Fact
r ranges from -1 to 1; r² gives the proportion of variance explained.