The Sunny Dale Bank monitors the time required to serve customers at the drive-through window becauseit is an important quality factor in competing with other banks in the city. After analyzing the data gathered inan extensive study of the window operation, bank management determined that the mean time to processa customer at the peak demand period is 5 minutes, with a standard deviation of 1.5 minutes. Managementwants to monitor the mean time to process a customer by periodically using a sample size of six customers. Assume that the process variability is in statistical control. Design an x-chart that has a type I error of5 percent. That is, set the control limits so that there is a 2.5 percent chance a sample result will fall below theLCL and a 2.5 percent chance that a sample result will fall above the UCL. After several weeks of sampling,two successive samples came in at 3.70 and 3.68 minutes, respectively. Is the customer service process instatistical control?
The Sunny Dale Bank monitors the time required to serve customers at the drive-through window because
it is an important quality factor in competing with other banks in the city. After analyzing the data gathered in
an extensive study of the window operation, bank management determined that the mean time to process
a customer at the peak demand period is 5 minutes, with a standard deviation of 1.5 minutes. Management
wants to monitor the mean time to process a customer by periodically using a
5 percent. That is, set the control limits so that there is a 2.5 percent chance a sample result will fall below the
LCL and a 2.5 percent chance that a sample result will fall above the UCL. After several weeks of sampling,
two successive samples came in at 3.70 and 3.68 minutes, respectively. Is the customer service process in
statistical control?
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