tive Statistics 14. Density The densities (in kilograms per cubic meter) of the ten mos abundant elements by weight in Earth's crust 1.4 2330 2700 7870 1500 970 900 1740 4500 0.09 1213 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 mothers 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 (b) 20- Frequency 5 10 15 Frequency 15 10 42 45 48 51 54 57 60 Data entry 42 45 48 51 54 57 60 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: 12/8 = 128 (b) 12 Key: 131=131 13 5 5 8 13 1 14 1 2 14 2 3 5 17 18 167 15 0067 15 0 4 5 6 8 16 4 5 9 16 1 2 3 3 3 1368 17 1 588 089 18 2 3 4 5 19 6 19 02 20 3 5 7 20