Help a-d

The table below contains the energy usage of 90 gas-heated homes. The variable reported is BTUumber of heating degree days. a. Calculate the sample mean and standard deviation of energy usage. b. Construct a histogram of the energy usage data and comment on the shape of the data distribution. c. Construct a stem-and-leaf diagram of energy usage. d. What proportion of the energy usage data is above the average usage plus 2 standard deviations? 7.87 9.43 7.16 8.67 12.31 9.84 16.90 10.04 12.62 7.62 11.12 13.43 9.07 6.94 10.28 9.37 7.93 13.96 6.80 4.00 8.58 8.00 5.98 15.24 8.54 11.09 11.70 12.71 6.78 9.82 12.91 10.35 9.60 9.58 9.83 9.52 18.26 10.64 6.62 5.20 12.28 7.23 2.97 8.81 9.27 11.29 8.29 9.96 10.30 16.06 14.24 11.43 10.28 13.60 5.94 10.36 6.85 6.72 10.21 8.61 11.62 11.21 10.95 7.62 10.40 12.92 15.12 13.47 8.47 11.70 7.73 8.37 7.29 10.49 8.69 8.26 7.69 12.19 5.56 9.76 7.15 12.69 13.38 13.11 10.50 14.35 13.42 6.35 9.83 12.16