3.39 Match the correlation. In this exercise you will use the Correlation and Regression applet to make scatterplots with 10 points that have correlation close to 0.7. The lesson here is that many patterns can have the same correlation. Always plot your data before you trust a correlation.

a. Stop after adding the first 2 points. What is the value of the correlation? Why does it have this value?

b. Create a lower-left to upper-right pattern of 10 points with correlation about r=0.7. (You can drag points up or down to adjust r after you have 10 points.) Make a rough sketch of your scatterplot.

c. Make another scatterplot with 9 points in a vertical stack at the left of the plot. Add 1 point far to the right, and then move it until the correlation is close to 0.7. Make a rough sketch of your scatterplot.

d. Make yet another scatterplot with 10 points in a curved pattern that starts at the lower left, rises to the right, and then falls again at the far right. Adjust the points up or down until you have a quite smooth curve with correlation close to 0.7. Make a rough sketch of this scatterplot.

Exercises marked with the Large Data Set icon guide you through the comprehensive analysis of more complex data sets characterized by a large number of observations, a number of variables, or both. You can find many more such exercises in the book’s review chapters (Chapters 8, 16, and 25). Short answers are not available for these exercises to enable their use for class work or assignments.