The National Bank of Warwick is concerned with com-plaints from customers about its drive-through window op-eration. Customers complain that it sometimes takes too long to be served and since there are often cars in front and back of a customer, they cannot leave if the service is tak-ing a long time. To correct this problem the bank installed an intercom system so the drive-through window teller cancall for assistance if the line backs up or a customer has an unusually long transaction. The bank’s objective is an aver-age customer’s waiting and service time of approximately 3 minutes. The bank’s operations manager wants to moni-tor the new drive-through window system with SPC. The manager has timed five customers’ waiting and servicetimes at random for 12 days as follows:Develop an -chart to be used in conjunction with anR-chart to monitor this drive-through window process andindicate if the process is in control using these charts. Observation Times (min)Sample 1 2 3 4 51 3.05 6.27 1.35 2.56 1.052 7.21 1.50 2.66 3.45 3.783 3.12 5.11 1.37 5.20 2.654 2.96 3.81 4.15 5.01 2.155 3.25 3.11 1.63 1.29 3.746 2.47 2.98 2.15 1.88 4.957 6.05 2.03 3.17 3.18 2.34
The National Bank of Warwick is concerned with com-
plaints from customers about its drive-through window op-
eration. Customers complain that it sometimes takes too
long to be served and since there are often cars in front and
back of a customer, they cannot leave if the service is tak-
ing a long time. To correct this problem the bank installed
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 aver-
age customer’s waiting and service time of approximately
3 minutes. The bank’s operations manager wants to moni-
tor the new drive-through window system with SPC. The
manager has timed five customers’ waiting and service
times at random for 12 days as follows:Develop an -chart to be used in conjunction with an
R-chart to monitor this drive-through window process and
indicate if the process is in control using these charts.
Observation Times (min)
Sample 1 2 3 4 5
1 3.05 6.27 1.35 2.56 1.05
2 7.21 1.50 2.66 3.45 3.78
3 3.12 5.11 1.37 5.20 2.65
4 2.96 3.81 4.15 5.01 2.15
5 3.25 3.11 1.63 1.29 3.74
6 2.47 2.98 2.15 1.88 4.95
7 6.05 2.03 3.17 3.18 2.34
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