A process that drills holes in crankshafts that are subseque

A process that drills holes in crankshafts that are subsequently ground has been found to be in good statistical control, with the following statistics used used to estimate the mean and variance of the hole diameter:

x (double bar on top) = 15.050 millimeters

R (bar on top) = 0.110 millimeters

It is also known that 95% of the hole diameters lie within the range 14.945 to 15.155 millimeters. Find the size of the samples employed to produce the ranges R used to estimate the standard deviation of the process. Assume that the hole diameters are normally distributed.

Solution