Is there evidence that the population mean delivery time has been reduced below the previous population mean?

Is there evidence that the population mean delivery time has been reduced below the previous population mean?

You are the manager of a restaurant that delivers pizza to college dorm rooms. You have just changed your delivery process in an effort to reduce the mean time between the order and completion of delivery from the current 25 minutes. A sample of 36 orders using the new delivery process yields a sample mean of 22.4 minutes and a sample standard deviation of 6 minutes.
1.Using the six-step critical value approach, at the 0.05 level of significance, is there evidence that the population mean delivery time has been reduced below the previous population mean value of 25 minutes? Please write out all 6 steps


 

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