The Lakeside Bank is concerned with complaints from customers about its drive-through window operation. Customers complain that it sometimes takes too long to be served. Since there are often cars in front of and behind a customer, they cannot leave if the service is taking a long time. To correct this problem, the bank installs an intercom system so the drive-through window teller can call for assistance if the line backs up or a customer has an unusually long transaction. The bank€™s objective is an average customer waiting and service time of approximately 3 minutes. The bank€™s operations manager wants to monitor the new drive-through window system with SPC. The manager times five customers€™ waiting and service times at random for 12 days as follows:

Develop an x¯-chart to be used in conjunction with an R-chart to monitor this drive-through window process and indi-cate if the process is in control using these charts.

Transcribed Image Text:

Sample Observation Times (min) 2 3 5 3.05 6.27 1.35 2.56 1.05 1.50 7.21 2.66 3.45 3.78 3.12 5.11 1.37 5.20 2.65 2.96 3.81 4.15 5.01 2.15 3.25 3.11 1.63 1.29 3.74 2.15 4.95 2.47 2.98 1.88 6.05 2.03 3.17 3.18 2.34 1.87 2.65 1.98 2.74 3.63 3.33 4.15 8.06 2.98 3.05 10 2.61 2.15 3.80 3.05 3.16 3.52 11 5.66 1.18 3.45 2.07 12 3.18 7.73 2.06 1.15 3.11 3. 4)