Question

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. Here is a summary of the results.

Ad source	n	x	s
Wall Street Journal	66	4.77	1.50
National Enquirer	61	2.43	1.64

Find the two-sample pooled t statistic. Then formulate the problem as an ANOVA and report the results of this analysis. Verify that F= t ².

Answer 1

Pooled StDev = 1.56876

Value of t statistic =   8.398358 ,  DF = 125

Formulating the above as ANOVA with two groups under equal variability, we compute the following ANOVA table

We find that t=8.398358 and t²= 70.5324 =F, as desired.

ANOVA suggests rejection of the null at 5% level.