Two types of plastic are suitable for use by an electronic calculator manufacturer. The breaking strength of this plastic is important. It is known that ????1 = ????2 = 1.0 psi. From random samples of n1 = 10 and n2 = 12, we obtain y1 = 162.5 and y2 = 155.0. The company will not adopt plastic 1 unless its breaking strength exceeds that of plastic 2 by at least 10 psi.

Based on the sample information, should they use plastic 1? In answering this question, set up and test appropriate hypotheses using ???? = 0.01. Construct a 99 percent confidence interval on the true mean difference in breaking strength.