A manufacturing firm has been averaging 18.2 orders per week for several years. But, throughout a recession, orders appeared to slow. Assume the firm's production manager randomly samples 32 weeks and finds a sample mean of 15.6 orders. The population standard deviation is 2.3 orders. Test to determine whether the average number of orders is down by using ? = .10.
The observed z = -6.39
And why do we fail to reject the null hypothesis?