A manufacturer of automobile shock absorbers is interested in comparing the durability of its shocks with that of its two biggest competitors. To make the comparison, a set of one each of the manufacturer’s and of the competitor’s shocks were randomly selected and installed on the rear wheels of each of six randomly selected cars of the same type. After the cars had been driven 20,000 miles, the strength of each test shock was measured, coded, and recorded.

Do these data present sufficient evidence to conclude there is a difference in the mean strength of the three types of shocks after 20,000 miles?