Many companies that cater to teenagers have learned that young people respond to commercials that provide dance-beat music, adventure, and a fast pace rather than words. In one test, a group of 128 teenagers were shown commercials featuring rock music, and their purchasing frequency of the advertised products over the following month was recorded as a single score for each person in the group.

Then a group of 212 teenagers was shown commercials for the same products, but with the music replaced by verbal persuasion. The purchase frequency scores of this group were computed as well. The results for the music group were x‾=23.5 and s = 12.2; and the results for the verbal group were x‾=18.0 and s = 10.5. Assume that the two groups were randomly selected from the entire teenage consumer population.

Using the α = 0.01 level of significance, test the null hypothesis that both methods of advertising are equally effective versus the alternative hypothesis that they are not equally effective. If you conclude that one method is better, state which one it is, and explain how you reached your conclusion.