Practice Another X Each of 15 refrigerators of a certain type has been returned to a distributor because of an audible, high-pitched, oscillating noise when the refrigerators are running. Suppose that 12 of these refrigerators have a defective compressor and the other 3 have less serious problems. If the refrigerators are examined in random order, let X be the number among the first O examined that have a defective compressor. (a) Calculate P(x = 7) and (X 7). (Reund your answers to four decimal places.) P(x =7) = [0.4753 | % [ 0.4747 P(x 7) = 5247 % [ 06593 (b) Determine the probability that X exceeds its mean value by more than 1 standard deviation. (Round your answer to four decimal places.) 84766 % [ o307 =