The U.S. Energy Information Administration compiles data on the U.S. energy industry. The file titled Energy contains data on the number of megawatt-hours of electricity sold in the United States to all customers, the average price per kilowatt-hour, the total number of customers, and the total volume of carbon dioxide emissions for the years 2005 2015 (www.eia.gov/electricity).

a. Produce a correlation matrix for the four variables. Predict which variable will be the first to enter the model if a forward stepwise approach is used to explain the variation in carbon dioxide emissions. Explain.

b. Use XLSTAT to run a forward stepwise model to maximize adjusted R2 with carbon dioxide as the dependent variable. Discuss the resulting model and associated statistics.
c. Discuss what steps you would take to improve this model.