Homer's Pizza, which predominantly delivers within the certain distance, has just changed its delivery process in an effort to reduce the mean time between the order and completion of delivery from the current 20 minutes. A sample of 49 orders using the new delivery process yield a sample mean of 22.5 minutes and a sample standard deviation of 3.5 minutes.
a) 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 20 minutes?
b) At the 0.01 level of significance, use the five step p-value approach. (hint: use PHStat or other means to calculate the p-value)
c) Compare your conclusions in (a) and (b).