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

a. With x = representative age and y = median distance walked in 6 minutes, construct a scatterplot. How does the pattern in the scatterplot for girls differ from the pattern in the scatterplot for boys from Exercise 5.29?
b. 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. y^ = 479.997 + 12.525x
c. Compute the five residuals and construct a residual plot. 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?

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