19. It has been suspected for some time that the morning shift is more efficient than the afternoon shift. Random observations yield the following data:

Morning shift : n1 = 5, ¯X1 = 22.9, S2 1 = 6.75 Afternoon shift : n2 = 7, ¯X2 = 21.5, S2 2 = 7.25 Assuming normality:

(a) Test the hypothesis σ2 1 = σ2 2 at the 1% level of significance.

(b) Using (a), test the hypothesis H0: μ1 = μ2 versus H1: μ1 > μ2.