60 Chapter 2 Graphical Summaries of Data a. How many classes are there? b. What is the class width? c. Which class has the highest frequency? d. What percentage of students are more than 72 inches tall? e. Is the histogram most accurately described as skewed to the right, skewed to the left, or approximately symmetric? 20. Trained rats: Forty rats were trained to run a maze. The following frequency histogram presents the numbers of trials it took each rat to learn the maze. 1 2 3 4 5 6 7 8 9 10 8 6 4 2 0 Frequency Number of Trials a. What is the most frequent number of trials? b. How many rats learned the maze in three trials or less? c. How many rats took nine trials or more to learn the maze? d. Is the histogram most accurately described as skewed to the right, skewed to the left, or approximately symmetric? 21. Batting average: The following frequency distribution presents the batting averages of Major League Baseball players who had 300 or more plate appearances during the 2010 season. Batting Average Frequency 0.180–0.199 3 0.200–0.219 8 0.220–0.239 22 0.240–0.259 72 0.260–0.279 80 0.280–0.299 47 0.300–0.319 28 0.320–0.339 6 0.340–0.359 2 Source: sports.espn.go.com a. How many classes are there? b. What is the class width? c. What are the class limits? d. Construct a frequency histogram. e. Construct a relative frequency distribution. f. Construct a relative frequency histogram. g. What percentage of players had batting averages of 0.300 or more? h. What percentage of players had batting averages less than 0.220? 22. Batting average: The following frequency distribution presents the batting averages of Major League Baseball players in both the American League and the National League who had 300 or more plate appearances during the 2010 season. Batting American League National League Average Frequency Frequency 0.180–0.199 2 1 0.200–0.219 4 4 0.220–0.239 14 8 0.240–0.259 34 38 0.260–0.279 35 45 0.280–0.299 21 26 0.300–0.319 15 13 0.320–0.339 3 3 0.340–0.359 2 0 Source: sports.espn.go.com a. Construct a frequency histogram for the American League. b. Construct a frequency histogram for the National League. c. Construct a relative frequency distribution for the American League. d. Construct a relative frequency distribution for the National League. e. Construct a relative frequency histogram for the American League. f. Construct a relative frequency histogram for the National League. g. What percentage of American League players had batting averages of 0.300 or more? h. What percentage of National League players had batting averages of 0.300 or more? i. Compare the relative frequency histograms. What is the main difference between the distributions of batting averages in the two leagues? 23. Time spent playing video games: A sample of 200 college freshmen was asked how many hours per week they spent playing video games. The following frequency distribution presents the results. Number of Hours Frequency 1.0 – 3.9 25 4.0 – 6.9 34 7.0 – 9.9 48 10.0 – 12.9 29 13.0 – 15.9 23 16.0 – 18.9 17 19.0 – 21.9 13 22.0 – 24.9 7 25.0 – 27.9 3 28.0 – 30.9 1 a. How many classes are there? b. What is the class width?
navidi_monk_essential_statistics_1e_ch1_3
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