(Chapter 8, STAT 1040)

# Correlation
## Scatter Diagrams
A scatter diagram or scatter plot shows the relationship between two variables. One variable is on the X axis, the other on the Y axis. 
### Association
- Positive association is demonstrated when the dots are trend upward as `x` increases. 
- Negative association is demonstrated when the the dots trend downward as `x` increases.
- Strong association is demonstrated when dots are clustered tightly together along a line.
- Weak association is demonstrated when dots are not clustered tightly. 
## Correlation
Correlation is between `-1` and `1`. Correlation near 1 means tight clustering, and correlation near 0 means loose clustering. 

# Terminology
| Term | Definition |
| `r` | Correlation Coefficient |