10.23 In tough economic times, the business staff at magazines are challenged to sell advertising space ...

      10.23 In tough economic times, the business staff at   magazines   are challenged to sell advertising space in their   publications.   Thus, one indicator of a weak economy is the   decline in   the number of “ad pages” that magazines have   sold. The   file contains the number of ad pages   found in the   May 2008 and May 2009 issues of 12 men’s   magazines.   (Data extracted from W. Levith, “Magazine   Monitor,”   Mediaweek, April 20, 2009, p. 53.)   a. At the   0.05 level of significance, is there evidence that   the mean   number of ad pages was higher in May 2008   than in May   2009?   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 interval   estimate of   the difference in the mean number of ad pages   in men’s   magazines between May 2008 and May 2009.    

      Magazine 2008 2009   Details 72.31 48.42   Esquire 66.69 42.79   Field & Stream 48.65 42.82   Flex 219.61 231.58   GQ 99.21 60.35   Maxim 68.5 41.82   Men's Fitness 99.43 67.63   Men's Health 90.88 74.45   Men's Journal 183.1 88.34   Mucscle & Fitness 169.63 198.93   Outdoor Life 41.39 30.16   Outside 126.97 103.58