Problem page an automobile assembly line operation has a scheduled mean completion time, , of minutes. the standard deviation of completion times is minutes. it is claimed that, under new management, the mean completion time has decreased. to test this claim, a random sample of completion times under new management was taken. the sample had a mean of minutes. assume that the population is normally distributed. can we support, at the level of significance, the claim that the mean completion time has decreased under new management? assume that the standard deviation of completion times has not changed