Chapter 17, Problem 71E

Home runs 2016 American League baseball teams play their games with the designated hitter rule, meaning that pitchers do not bat. The league believes that replacing the pitcher, traditionally a weak hitter, with another player in the batting order produces more runs and generates more interest among fans. Below are the average numbers of home runs hit per game in American League and National League stadiums for the 2016 season. (Data in Baseball 2016)

American		National
1.56	1.23	1.17	1.35
1.28	1.13	0.76	0.99
1.04	1.04	1.24	0.95
1.15	1.38	1.01	1.09
1.31	1.33	1.26	0.80
1.22	1.33	1.17	1.39
0.91	1.36	0.80	1.25
0.96		1.20

1. a) Create an appropriate display of these data. What do you see?
2. b) With a 95% confidence interval, estimate the mean number of home runs hit in American League games.
3. c) Coors Field, in Denver, stands a mile above sea level, an altitude far greater than that of any other major league ballpark. Some believe that the thinner air makes it harder for pitchers to throw curve balls and easier for batters to hit the ball a long way. Do you think the 1.26 home runs hit per game at Coors is unusual? (Denver is a National League team.) Explain.
4. d) Explain why you should not use two separate confidence intervals to decide whether the two leagues differ in average number of runs scored.
5. e) Using a 95% confidence interval, estimate the difference between the mean number of home runs hit in American and National League games.
6. f) Interpret your interval.
7. g) Does this interval suggest that the two leagues may differ in average number of home runs hit per game?