Sherri Welch is a quality control engineer with the windshield wiper manufacturing division of Emsco, Inc. Emsco is currently considering two new synthetic rubbers for its wiper blades, and Sherri was charged with seeing whether blades made with the two new compounds wear equally well. She equipped 12 cars belonging to other Emsco employees with one blade made of each of the two compounds. On cars 1 to 6, the right blade was made of compound A and the left blade was made of compound B; on cars 7 to 12, compound A was used for the left blade. The cars were driven under normal operating conditions until the blades no longer did a satisfactory job of clearing the windshield of rain. The data below give the usable life (in days) of the blades. At α = 0.05, do the two compounds wear equally well?.

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