Question

7.78 Does ad placement matter? Corporate advertising tries to enhance the image of the corporation. A study compared two ads from two sources, the Wall Street Journal and the National Enquirer. Subjects were asked to pretend that their company was considering a major investment in Performax, the fictitious sportswear firm in the ads. Each subject was asked to respond to the question “How trustworthy was the source in the sportswear company ad for Performax?” on a 7-point scale. Higher values indicated more trustworthiness. 38 Here is a summary of the results: Ad source Wall Street Journal National Enquirer n x ̄ s 66 4.77 1.50 61 2.43 1.64 (a) Compare the two sources of ads using a t test. Be sure to state your null and alternative hypotheses, the test statistic with degrees of freedom, the P-value, and your conclusion. (b) Give a 95% confidence interval for the difference. (c) Write a short paragraph summarizing the results of your analyses.

Answer 1

Let denote the mean rating for Wall Street Journal and National Enquirer respectively.

a)

b)

Since the confidence interval does not include 0, so at 95% level of confidence or at 5% level of significance, we can conclude that there is significant difference in mean ratings published in Wall Street Journal and National Enquirer.