12.4.20 Use the five numbers 15, 14, 18, 12, and 11 ( to complete parts a) through e) below. a) Compute the mean and standard deviation of the given set of data. The mean is x = 14 and the standard deviation is s = 2.74 . (Round to two decimal places as needed.) b) Add 15 to each of the numbers in the original set of data and compute the mean and the standard deviation of this new set of data. The new mean is x = and the new standard deviation is s = (Round to two decimal places as needed.)