T-Test with two samples with different variance
10-22 (3rd edition) 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 xbar1=290 and sig1=12, while another random sample of 16 gears from the second supplier results in xbar2=321 and sig2=22. (a) Is there evidence to support the claim that supplier 2 provides gears with higher mean impact strength? Use alpha=0.05 and assume that 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).