Two suppliers manufacture a plastic gear used in a laser printer. The impact strength of these gears measured in foot-pounds is an important characteristic. A random sample of 10 gears from supplier 1 results in and s1 = 12, while another random sample of 16 gears from the second supplier results in and s = 22.
(a) Is there evidence to support the claim that supplier 2 provides gears with higher mean impact strength? Use a = 0.05, and assume that both populations are normally distributed but the variances are not equal.
(b) What is the P-value for this test?
(c) Do the data support the claim that the mean impact strength of gears from supplier 2 is at least 25 foot-pounds higher than that of supplier 1? Make the same assumptions as in part (a).