Section 4.1 Summary

1. For two quantitative variables, scatterplots summarize the relationship by plotting all the $(x,y)$ points.
2. The correlation coefficient $r$ is a measure of the strength of linear association between two numeric variables. Values of $r$ close to 1 indicate that the variables are positively correlated. Values of $r$ close to −1 indicate that the variables are negatively correlated. Values of $r$ close to 0 indicate that the variables are not linearly correlated.