Q

a) The mean life of stockings used by an army was 30 days, with a standard deviation of 5

days. Assume the life of the stockings follows a normal distribution. If 100,000 pairs are

issued, use the unit normal distribution area table to find that how many would need

replacement before 35 days?

b) Let X be normally distributed with mean and standard deviation . So that P(X 45) =

0.90 and P(X 84) = 0.05. Use the unit normal distribution area table to find and .

c) An engineer is designing the interior doors in a shopping mall. He wants to make high

enough so that 85 percent of the people using the doors will have at least a one foot

clearance. Assuming that the heights will be normally distributed, with a mean of 70 inches

and a standard deviation of 3 inches, use the unit normal distribution area table to find how

high the engineer must make the doors?