A&A Enterprises ships integrated circuits to companies that assemble computers. Because computer manufacturing operations run on little inventory, parts must be available when promised. Thus, a critical element of A&A's customer satisfaction is on-time delivery performance. To ensure that their delivery process is performing as intended, a quality improvement team decided to monitor the firm's distribution and delivery process. From the A&A corporate data base, 100 monthly shipping records were randomly selected for the previous 21 months, and the number of on-time shipments was counted.
Month On Time
Develop the appropriate 3-sigma control chart(s) for monitoring this process. Does it appear that the delivery process is in control? If not, can you suggest some possible assignable causes?
The solution answers the question below.