Answer to Question #62103 in Statistics and Probability for kenneth Alex

Question

Each of 12 refrigerators of a certain type has been returned to a distributor because of an audible, high-pitched, oscillating noise when the refrigerator is running. Suppose that 7 of these refrigerator have defective compressor and the other 5 have less serious problems. If the refrigerators are examined in random order. Let X be the number among the first 6 examined that have a defective compressor. What is the probability that X exceeds its mean value by more than 1 standard deviation
0.132
0.121
0.112
0.651

4 The error involved in making a certain measurement is a continuous rv X with pdf
f(x)={0.09375(4−x2),−2≤x≤2
0,otherwise
compute P(-1<X
0.6875
0.3425
0.3662
0.5522