The diameter of bushings turned out by a manufacturing process is a normally distributed random variable with a mean of 4.035 mm and a standard deviation of 0.005 mm. A sample of 25 bushings is taken once an hour.
(a) Within what interval should 95 percent of the bushing diameters fall?
(b) Within what interval should 95 percent of the sample means fall?
(c) What conclusion would you reach if you saw a sample mean of 4.020? A sample mean of 4.055?