Almost all U.S. light-rail systems use electric cars that run on tracks built at street level. According to the Federal Transit Administration, light-rail is one of the safest modes of travel, with an accident rate of .99 accidents per million passenger miles as compared to 2.29 for buses. The following data show the miles of track and the weekday ridership in thousands of passengers for selected light-rail systems (USA Today, January 7, 2003).

a. Develop a scatter diagram for these data, treating the number of miles of track as the independent variable. Does a simple linear regression model appear to be appropriate?
b. Use a simple linear regression model to develop an estimated regression equation to predict the weekday ridership given the miles of track. Construct a standardized residual plot. Based upon the standardized residual plot, does a simple linear regression model appear to be appropriate?
c. Perform a logarithmic transformation on the dependent variable. Develop an estimated regression equation using the transformed dependent variable. Do the model assumptions appear to be satisfied by using the transformed dependent variable?
d. Perform a reciprocal transformation on the dependent variable. Develop an estimated regression equation using the transformed dependent variable.
e. What estimated regression equation would you recommend? Explain.

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