Algebra 1 / Unit 10: Data and Statistics
10.4 Scatter Plots and Correlation
Notes
A scatter plot shows pairs of numerical data as points.
- Positive correlation: $y$ tends to increase as $x$ increases. Negative: $y$ tends to decrease. None: no pattern.
- The correlation coefficient $r$ is between $-1$ and 1. Close to $\pm 1$ means a strong linear relationship; close to 0 means weak.
- Correlation does not prove causation. Ice cream sales and sunburns rise together because of a third factor, hot weather.
Practice
Hours studied and test scores tend to rise together. That is:
Both increase together.
Which $r$ shows the strongest linear relationship?
Strength depends on how close $|r|$ is to 1.
Towns with more firefighters have more fire damage. The best explanation is:
A third variable, fire size, drives both.
Ready for more? Take the Unit 10 test.