A new purification unit is installed in a chemical process. Before its installation, a random sample yielded the following data about the percentage of impurity: x12  9.85,s12  6.79 and n1 10 . After installation, a random sample resulted in x22  8.08,s22  6.18 and n2  8.
(a) Can you conclude that the two variances are equal? Use  =0.05.
(b) Can you conclude that the new purification device has reduced the mean percentage of impurity? Use a = 0.05.