A manufacturer of automobile tires believes it has developed a new rubber compound that has superior antiwearing qualities. It produced a test run of tires made with this new compound and had them roadteste
d. The data values recorded were the amount of tread wear per 10,000 miles. In the past, the mean amount of tread wear per 10,000 miles, for tires of this quality, has been 0.0625 inch. The null hypothesis to be tested here is “The mean amount of wear on the tires made with the new compound is the same mean amount of wear with the old compound, 0.0625 inch per 10,000 miles,”Ho: µ = 0.0625. Three possible alternative hypotheses could be used: (1) Ha: µ < 0.0625, (2) Ha: µ ≠ 0.0625, (3) Ha: µ > 0.0625.
a. Explain the meaning of each of these three alternatives.
b. Which one of the possible alternative hypotheses should the manufacturer use if it hopes to conclude that “use of the new compound does yield superior wear”?