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 s2  22.

(a) Is there evidence to support the claim that supplier 2 provides gears with higher mean impact strength? Use

  0.05, and assume that both populations are normally distributed but the variances are not equal. What is the P-value for this test?

(b) 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).

(c) Construct a confidence interval estimate for the difference in mean impact strength, and explain how this interval could be used to answer the question posed regarding supplierto-supplier differences.