1. Foreclosure rates. Home foreclosures were up 47% in March 2008 compared to the previous year (realestate.msn.com; April 2008). The data show home foreclosure rates (as % change from the previous year) for a sample of cities in two regions of the United States, the Northeast and the Southwest.
2. Baseball 2006. 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 runs scored (per game by both teams) in American League and National League stadiums for the 2006 season.
Northeast: 2.99,- 2.36, 3.03, 1.01, 5.77, 9.95, - 3.52, 7.16, - 3.34, 4.75, 5.25, 6.21, 1.67, - 2.45, 4.50, 1.87, - 2.15, - 0.75 - 0.55, 3.45,
Southwest: 10.15, 23.05, 18.95, 21.16, 17.45, 12.67, 13.75, 29.42, 11.45, 16.77, 12.67, 13.69, 25.81, 21.16, 19.67, 11.88, 13.67, 18.00, 12.88
a) Write the null and alternative hypotheses.
b) Check the conditions for a Wilcoxon rank-sum (or Mann-Whitney) test.
c) Complete the test and report your conclusion.
d) Make histograms of each group. Discuss whether you would choose a nonparametric test for these data or a two-sample t-test (as in Chapter 14 Exercise 36.)