A new production process is being contemplated for the manufacture of stainless steel bearings.
Measurements of the diameters of random samples of bearings from the old and the new processes produced the following data:
Old 16.3 15.9 15.8 16.2 16.1 16.0 15.7 15.8
15.8 15.7 15.8 15.7 15.9 16.1 16.3 16.1
New: 15.9 16.2 16.0 15.8 16.1 16.1 15.8 16.0
15.8 15.8 16.2 16.3 16.2 15.9 15.7 16.2
(a) Can you conclude at the 5% level that the new process yields a higher mean size bearing than the old one?
(b) Find a 90% confidence interval for the difference between the mean size bearing of the two processes.