In tough economic times, the business staff atmagazines are

10.23 In tough economic times, the business staff atmagazines are challenged to sell advertising space in theirpublications. 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 thatthe mean number of ad pages b. What assumption is necessary about the populationdistribution in order to perform this test?

c. Use a graphical method to evaluate the validity of theassumption 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.