5.31 ● The paper referenced in the previous exercise also gave the 6-minute walk distances for 248 girls age 3 to 18 years. The median 6-minute walk times for girls for the five age groups were 492.4 578.3 655.8 657.6 660.9

a. With x 5 representative age and y 5 median distance walked in 6 minutes, construct a scatterplot.

b. How does the pattern in the scatterplot for girls differ from the pattern in the scatterplot for boys from Exercise 5.30?

c. Find the equation of the least-squares regression line that describes the relationship between median distance walked in 6 minutes and representative age for girls.

d. Compute the five residuals and construct a residual plot.

e. The authors of the paper decided to use a curve rather than a straight line to describe the relationship between median distance walked in 6 minutes and age for girls. What aspect of the residual plot supports this decision? (Hint: See Example 5.8.)