The article Air Pollution and Medical Care Use by Older Americans(Health Affairs [ 2002]: 207 214) gave

The article €œAir 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:

The equation of the least squares regression line for this data set is ˆ = 1082.2 2 4.691x, where y = medical cost and x = pollution.
a. Compute the six residuals.
b. What is the value of the correlation coefficient for this data set? Does this value indicate that the linear relationship between pollution and medical cost is strong, moderate, or weak? Explain.
c. Construct a residual plot. Are there any unusual features of the residual plot?
d. The observation for the West, (40.0, 899), is far removed from the other values in the sample. Is this observation influential in determining the values of the slope and/ or intercept of the least squares line? Justify your answer.

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