The article “Air Pollution and Medical Care Use by Older Americans” (Health Affairs [2002]:

207–214) gave data on a measure of pollution (in micrograms of particulate matter per cubic meter of air) and the cost of medical care per person over age 65 for six geographical regions of the United States:

Region Pollution Cost of Medical Care North 30.0 915 Upper South 31.8 891 Deep South 32.1 968 West South 26.8 972 Big Sky 30.4 952 West 40.0 899

a. Construct a scatterplot of the data. Describe any interesting features of the scatterplot.

b. Find the equation of the least-squares line describing the relationship between y 5 medical cost and x 5 pollution. y^ 5 1082.24 2 4.691x

c. Is the slope of the least-squares line positive or negative? Is this consistent with your description of the relationship in Part (a)?

d. Do the scatterplot and the equation of the leastsquares line support the researchers’ conclusion that elderly people who live in more polluted areas have higher medical costs? Explain.