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 ‾x1=289.30 and s1=22.5s and another random sample of 16 gears from the second supplier results in xbar2=321.50 and s2=21
(a) Is there evidence to support the claim that supplier 2 provides gears with higher mean impact strength? Use the P-value approach, and assume that both populations are normally distributed but the variances are not equal.
(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 an appropriate 95% CI on the difference in mean impact strength. Use this interval to answer the question posed in part (b).