Household energy expenditure. Refer to the annual total household expenditure on energy from 2011 to 2020, Exercise 11.29 (p. 661). The annual total household expenditure (in £ millions) data on gas, on electricity, on liquid fuels, and the total of individual household’s expenditure on energy are saved in the ENERGY file. Information from first two and last two rows are listed in the accompanying table. Consider a first-order multiple regression model to predict the total expenditure (y) by using the gas (x1), electricity (x2), and liquid fuels (x3).

a. Use statistical software to fit the model to the data. Give the least squares prediction equation.

b. Find and give a practical interpretation of the standard deviation of the model, s.

c. Find and give a practical interpretation of the coefficient of determination, R2 .

d. Conduct a test of the overall adequacy of the model using a = .10.

e. Find a 95% confidence interval for the b coefficient associated with expenditure on gas (in £ millions) (x1). Interpret the result.