1) Find the following probabilities:
a) P (0 ≤ Z ≤ .5)
b) P (Z ≤ .5)
c) P (Z ≤ -.5)
d) P (Z ≥ .5)
e) P (- .5 ≤ Z ≤ .5)
2) Dearborn Tech produces a circuit board that has an average life span of 4,500 hours. The life span is normally distributed with a standard deviation of 500 hours. The firm is considering a 3,800 hours' warranty on the circuit board. If this warranty policy is adopted, what proportion of circuit boards should the firm expect to replace under warranty?