In the July 1989 issue of Quality Progress. William J. McCabe discusses using a p chart to study a company's order entry system. The company was experiencing problems meeting the promised 60-day delivery schedule. An investigation found that the order entry system frequently lacked all the information needed to correctly process orders. Figure 17.25 gives a p chart analysis of the percentage of orders having missing information.
a. From Figure 17.25 we see that  = .527. If the subgroup size for this p chart is n = 250, calculate the upper and lower control limits, UCL and LCL.
b. Is the p chart of Figure 17.25 in statistical control? That is, are there any assignable causes affecting the fraction of orders having missing information?
c. On the basis of the p chart in Figure 17.25, McCabe says,
The process was stable and one could conclude that the cause of the problem was built into the system. The major cause of missing information was sales people not paying attention to detail, combined with management not paying attention to this problem. Having sold the product, entering the order into the system was generally left to clerical people while the salespeople continued selling.
Can you suggest possible improvements to the order entry system?