18 20 35 30 20 36 25 22 27 15 20 19 15 24 12 24 28 27 15 21 21 15 20 15 11 15 1720 31 12 21 30 15 18 13 12 35 38 11 24 30 24 22 12 12 18 30 25 12 32 25 14 17 2115 27 15 20 22 25 18 8 10 12 12 14 41 25 29 33 24 40 30 55 35 43 12 12 58 95 2432 18 15 23 18 26 44 16 22 25 32 30 17 20 20 40 22 20 15 18 20 48 25 22 36 13 36

The tallest dam in the world is the 1001-ft-high Jinping-I Dam constructed on the ver Yalong in China. Its primary purpose is to generate hydroelectric power. There are approximately 300 public utility dams in the United States. A random sample of these dams was obtained and the ight (in feet) of each was recorded. 18 20 35 30 20 36 25 22 27 15 20 19 15 24 12 24 28 27 15 21 21 15 20 15 11 15 17 Dam 20 31 12 21 30 15 18 13 12 35 38 11 24 eight | 30 24 22 12 12 18 30 25 12 32 25 14 17 21 (ft) 15 27 15 20 22 25 18 8 10 12 12 14 41 25 29 33 24 40 30 55 35 43 12 12 58 95 24 32 18 15 23 18 26 44 16 22 25 32 30 17 20 20 40 22 20 15 18 20 48 25 22 36 13 36 [4 = 1, 2, 1 marks] Find the mean, variance, and standard deviation. Leave answers to four decimal places. [4 = 3, 1 marks] Find the proportion of observations within 1, 2, and 3 standard deviations about the mean. Leave answers to two decimal places. Use these proportions to determine whether the