STAT 113 Scatterplots and Correlation Colin Reimer Dawson Oberlin College September 15, 2017 1 / 8
The Scatterplot • With two quantitative values from the same source (e.g. from the same person), we can represent each case (e.g., person) as a point in 2D space. • If we plot all of these points, we obtain a scatterplot 2 / 8
Scatter Diagrams Show Patterns Do you see a pattern? 3 / 8
Correlation • You can identify correlations on a scatter diagram by the distinct patterns they form. • The variables are said to have a linear association if the scatter diagram shows the points clustered around an approximately straight line. • (Pearson’s) correlation coefficient measures the strength and direction of this association. 4 / 8
Positive Linear Association 5 / 8
Negative Linear Association 6 / 8
No Association 7 / 8
Estimating Relationships Handout 8 / 8
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