An electronics manufacturing process has historically had a mean completion time of 75 minutes. It is claimed that, due to improvements in the process, the mean completion time,, is now less than 75 minutes. A random sample of 18 completion times using the new process is taken. The sample has a mean completion time of 71 minutes, with a standard deviation of 8 minutes.

Assume that completion times using the new process are approximately normally distributed. At 0.10 the

level of significance, can it be concluded that the population mean completion time using the new process is less than

minutes?

Perform a one-tailed test.