A study of the effect of television   commercials on 12-year-old children measured their attention span, in   seconds. The commercials were for clothes, food, and toys. At the .05   significance level is there a difference in the mean attention span of the   children for the various commercials? Are there significant differences   between pairs of means? Would you recommend dropping one of the three   commercial types?        Cloth Food Toys   26 45 60   21 48 51   43 43 43   35 53 54   28 47 63   31 42 53   17 34 48   31 43 58   20 57 47   47 51    44 51    54