The in-control mean of the inside diameter of an 'O' ring is 1.426" and the in-control standard deviation is 0.0010". The inside diameters are normally distributed.
(a) What are the control limits of the X chart, if α = 0.0026 and the sample size is 4 ?
(b) Find the proportion of rejected 'O' rings when the process is in control, if the tolerance limits are
1.426 ± 0.0015.