The file Energy contains the per capita energy consumption, in kilowatt- hours, for each of the 50 states and the District of Columbia during a recent year.

a. Compute the mean, variance, and standard deviation for the population.

b. What proportion of these states has per capita energy consumption within ± 1 standard deviation of the mean, within ± 2 standard deviations of the mean, and within ± 3 standard deviations of the mean?

c. Compare your findings with what would be expected based on the empirical rule. Are you surprised at the results in (b)?

d. Repeat (a) through (c) with the District of Columbia removed. How have the results changed?