Steel rods, manufactured with a nominal diameter of 3 cm, are considered acceptable if the diameter falls within the limits of 2.99 and 3.01 cm. It is observed that about 5% are rejected oversize and 5% are rejected undersize.
Assuming that the diameters are normally distributed, find the standard deviation of the distribution. Compute the proportion of rejects if the permissible limits are changed to 2.985 and 3.015 cm