94 CHAPTER 2 Descriptive Statistics 14. Density The densities (in kilograms per cubic meter) of the ten most abundant elements by weight in Earth’s crust 1.4 2330 2700 7870 1500 970 900 1740 4500 0.09 Finding Sample Statistics In Exercises 15 and 16, find the range, mean, variance, and standard deviation of the sample data set. 15. Ages of Students The ages (in years) of a random sample of students in a campus dining hall 19 20 17 19 17 21 23 21 17 17 19 19 17 20 23 18 18 18 18 19 16. Pregnancy Durations The durations (in days) of pregnancies for a random sample of pregnant people 277 291 295 280 268 278 291 277 282 279 296 285 269 293 267 281 286 269 264 299 275 17. Estimating Standard Deviation Both data sets shown in the histograms have a mean of 50. One has a standard deviation of 2.4, and the other has a standard deviation of 5. By looking at the histograms, which is which? Explain your reasoning. (a) 20 15 10 5 42 45 48 51 54 57 60 Frequency Data entry (b) 20 15 10 5 42 45 48 51 54 57 60 Frequency Data entry 18. Estimating Standard Deviation Both data sets shown in the stem-and-leaf plots have a mean of 165. One has a standard deviation of 16, and the other has a standard deviation of 24. By looking at the stem-and-leaf plots, which is which? Explain your reasoning. (a) 12 8 9 Key: 120 8 = 128 13 5 5 8 14 1 2 15 0 0 6 7 16 4 5 9 17 1 3 6 8 18 0 8 9 19 6 20 3 5 7 (b) 12 Key: 130 1 = 131 13 1 14 2 3 5 15 04568 16 112333 17 1 5 8 8 18 2 3 4 5 19 0 2 20 19. Salary Offers You are applying for jobs at two companies. Company A offers starting salaries with m = $41,000 and s = $1000. Company B offers starting salaries with m = $41,000 and s = $5000. From which company are you more likely to get an offer of $43,000 or more? Explain your reasoning.
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