A critical dimension of the service quality of a deposit collection booth is the waiting time of a transaction to get money from the employee. Periodically, random samples of four customer are measured for waiting time. The results of the last five samples are in the following table: Sample Time (sec) from Four Customers 1 525 510 495 514 2 512 520 508 524 3 505 458 504 505 4 450 495 521 512 5 498 510 480 521 Required: i. Assuming that the management is willing to use three-sigma control limits and using only historical information of the standard deviation of the process distribution is 6.85 that contained in the five samples, show that the ATM Booth waiting time is in statistical control. ii. Suppose that the standard deviation of the process distribution is 6.85. If the specification for the waiting time are 510±35sec., is the process capable? Why or why not? Assume Three sigma performance is desired by the management.
6. A critical dimension of the service quality of a deposit collection booth is the waiting time of a
transaction to get money from the employee. Periodically, random samples of four customer are
measured for waiting time. The results of the last five samples are in the following table:
Sample Time (sec) from Four Customers
1 525 510 495 514
2 512 520 508 524
3 505 458 504 505
4 450 495 521 512
5 498 510 480 521
Required:
i. Assuming that the management is willing to use three-sigma control limits and using only
historical information of the standard deviation of the process distribution is 6.85 that
contained in the five samples, show that the ATM Booth waiting time is in statistical control.
ii. Suppose that the standard deviation of the process distribution is 6.85. If the specification for
the waiting time are 510±35sec., is the process capable? Why or why not? Assume Three
sigma performance is desired by the management.
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