Question 20.38

474 CHAPTER 20 Inference about a Population Mean 20.38 Kicking a helium-filled football. Does a football filled with helium travel farther than one filled with ordi- (a) nary air? To test this, the Columbus Dispatch conducted a study. Two identical footballs, one filled with helium and one filled with ordinary air, were used. A casual (b) observer was unable to detect a difference in the two footballs. A novice kicker was used to punt the foot- balls. A trial consisted of kicking both footballs in a (c) random order. The kicker did not know which foot- ball (the helium-filled or the air-filled football) he was kicking. The distance of each punt was recorded. 20.40 Fu Then another trial was conducted. A total of 39 trials of were run. Here are the data for the 39 trials, in yards & that the footballs traveled. The difference (helium m minus air) is the response variable. 25 E FTBALL Helium 25 16 14 23 29 ar 25 26 22 26 Air 25 23 18 16 35 15 26 24 24 28 Difference 0 - 7 7 -2-12 14 -1 2 - 2 - 2 Helium 12 28 28 31 22 29 23 26 35 24 Air 25 19 27 25 34 26 20 22 33 29 Difference - 13 9 1 6 -12 3 3 4 2 -5 Helium 31 34 39 32 14 28 30 27 33 11 Air 31 27 22 29 28 29 22 31 25 20 Difference 0 7 17 3 -14 -1 8 -4 8 -9 Helium 26 32 30 29 30 29 29 30 26 Air 27 26 28 32 28 25 31 28 28 Difference -1 6 2 -3 2 4 - 2 2 - 2 (a) Examine the data. Is it reasonable to use the t procedures? (b) If your conclusion in part (a) is Yes, do the data give convincing evidence that the helium-filled football travels farther than the air-filled football? di- 20.41