Chapter 7-Scatterplots, Association, and Correlation

Chapter 7-Scatterplots, Association, and Correlation

1. Scatterplots

   • relationship between two quantitative variables measured on the same cases.

2. Association

   • Direction
     • A positive direction or association means that, in general, as one variable in- creases, so does the other.
   • Form
     • most is straight, but you should certainly describe other patterns you see in scatterplots.
   • Strength
     • A scatterplot is said to show a strong association if there is little scatter around the underlying relationship.

3. Response variable, Explanatory variable, x-variable, y-variable

   • Assign to the y-axis the response variable that you hope to predict or explain. Assign to the x-axis the explanatory or predictor variable that accounts for, explains, predicts, or is otherwise responsible for the y-variable.

4. Correlation Coefficient

   • a numerical measure of the direction and strength of a linear association.

5. Lurking variable

   • A variable other than x and y that simultaneously affects both variables, accounting for the correlation between the two.

6. Outlier