Question: For one of the tasks in a manufacturing process, the mean time for task completion has historically been 35.0 minutes, with a standard deviation of 2.5 minutes. Workers have recently complained that the machinery used in the task is wearing out and slowing down. In response top the complaints, plant engineers have measured the time required for a sample consisting of 100 task operations. The 100 sample times, in minutes, are in data file XR09022 . Using the mean for this sample, and assuming that the population standard deviation has remained unchanged at 2.5 minutes, construct the 95% confidence interval for the population mean. Is 35.0 minutes within the confidence interval? Interpret your "yes" or "no" answer in terms of whether the mean time fore the task may have changed.

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