In tough economic times, the business staff atmagazines are challenged to sell advertising space in their publications. Thus, one indicator of a weak economy is thedecline in the number of "ad pages" that magazines havesold. The file contains the number of ad pagesfound in the May 2008 and May 2009 issues of 12 men'smagazines. (Data extracted from W. Levith, "MagazineMonitor," Mediaweek, April 20, 2009, p. 53.)
a. At the 0.05 level of significance, is there evidence that the mean number of ad pages
b. What assumption is necessary about the population distribution in order to perform this test?
c. Use a graphical method to evaluate the validity of the assumption in (b).
d. Construct and interpret a 95% confidence intervalestimate of the difference in the mean number of ad pagesin men's magazines between May 2008 and May 2009.