An article in the Journal of Environmental Engineering (Vol. 115, No. 3,1989, pp. 608-619) reported the results of a study on the occurrence of sodium and chloride in surface streams in central Rhode Island. The following data are chloride concentration y (in milligrams per liter) and roadway area in the watershed x (in percentage).
a) Draw a scatter diagram of the data. Does a simple linear regression model seem appropriate here?
b) Fit the simple linear regression model using the method of least squares.
c) Find an (unbiased) estimate of σ_{2}.
d) Estimate the mean chloride concentration for a watershed that has 1% roadway area.