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 torespond 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:


Wall Street Journal- N= 66 Mean = 4.77 s=1.50
National Enquierer- N=61 Mean= 2.43 s=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 df, the p-value, and your conclusion.

Answer 1

The summary table as shown below Standard viato Group n Mean source664.771.5 source612.431.64 a) Let u, denote the Population mean of Wall Street Journal trustworthy Let u, denote the Population mean ofNational Enquirer trustworthy The null and altemative hypotheses are Assume the Level of the significance, a 0.05 T est statistics: Under the null hypothesis the test stati stic is, 1.501 (1.64 61 The degres of freedom is, 61 of 121 1.50 1.64 61 66-1 61-1 P -value: Using excel function the P-value is, P-value-TDIST(x,alf,tailed) TDIST(837,1212) -0.0000 Decision & conclusion: Here, it can be observed that the P-value is less than the level of the significance 0.05, so the null hypotheses should be be rejected Therefore, it can be concluded that there is sufficent evidance to support that the two means are not equal b) Find the 95% confidence interval for the difference The level of the significance, c- 0.05 Using excel function the critical value is os 221 - T.INV 2T(0.05,121) +1.9798 THe 95% confidence intervals for difference ofmeans is, (X-5)tta 4.77-2.43)+19798 = 234 ±(1.9798)(0.2796) 1.786,2.894) Lower limit is 1.786 Uppere limit is 2.894