Might another measure of variability be better to compare luxury and budget hotel

Mercury Concentration ngg dry weight Site 1 Site 2 Year Calvi Marseilles-Coriou 1992 14.8 70.2 1991 12.9 160.5 1990 18.0 102.8 1989 8.7 100.3 1988 18.3 103.1 1987 10.3 129.0 1986 19.3 156.2 1985 12.7 117.6 1984 15.2 170.6 1983 24.6 139.6 1982 21.5 147.8 1981 18.2 197.7 1980 25.8 262.1 1979 11.0 123.3 1978 16.5 363.9 1977 28.1 329.4 1976 50.5 542.6 1975 60.1 369.9 1974 96.7 705.1 1973 100.4 462.0 1972 556.1 1971 461.4 1970 628.8 1969 489.2

a. Generate a time-series plot of the mercury concentrations and place lines for both

sites on the same graph. Comment on any trends in the lines across the years of data. Are the trends similar for both sites?

b. Select the most appropriate measure of center for the mercury concentrations. Compare

the center for the two sites.

c. Compare the variability in mercury concentrations at the two sites. Use the CV in

your comparison and explain why it is more appropriate than using the standard deviations.

d. When comparing the center and variability of the two sites, should the years

1969 –1972 be used for site 2?

3.6 The Boxplot

Basic 3.33 Find the median and the lower and upper quartiles for the following measurements: 13, 21, 9, 15, 13, 17, 21, 9, 19, 23, 11, 9, 21. Med. 3.34 The number of persons who volunteered to give a pint of blood at a central donor center was recorded for each of 20 successive Fridays. The data are shown here: 320 370 386

334 325

315 334 301 270 310 274 308 315 368 332 260 295 356 333 250 a. Construct a stem-and-leaf plot. b. Construct a boxplot and describe the shape of the distribution of the number of persons donating blood. Bus. 3.35 Consumer Reports in its May 1998 issue provides cost per daily feeding for 28 brands of dry dog food and 23 brands of canned dog food. Using the Minitab computer program, the side- by-side boxplot for these data follow.

a. From these graphs, determine the median, lower quartile, and upper quartile for the

daily costs of both dry and canned dog food.

b. Comment on the similarities and differences in the distributions of daily costs for the

two types of dog food. 3.7 Summarizing Data from More Than One Variable: Graphs and Correlation Soc. 3.36 For the homeownership rates given in Exercise 3.11, construct separate boxplots for the years 1985, 1996, and 2002. a. Describe the distributions of homeownership rates for each of the 3 years. b. Compare the descriptions given in part a to the descriptions given in Exercise 3.11. Soc. 3.37 Compute the mean, median, and standard deviation for the homeownership rates given in Exercise 3.11. a. Compare the mean and median for the 3 years of data. Which value, mean or median, is most appropriate for these data sets? Explain your answers.

b. Compare the degree of variability in homeownership rates over the 3 years. Soc.

3.38 For the boxplots constructed for the homeownership rates given in Exercise 3.36, place the three boxplots on the same set of axes.

a. Use this side-by-side boxplot to discuss changes in the median homeownership rate

over the 3 years.

b. Use this side-by-side boxplot to discuss changes in the variation in these rates over the

3 years. c. Are there any states that have extremely low homeownership rates? d. Are there any states that have extremely high homeownership rates? Soc. 3.39 In the paper “Demographic implications of socioeconomic transition among the tribal populations of Manipur, India’’ [Human Biology 1998 703: 597– 619], the authors describe the tremendous changes that have taken place in all the tribal populations of Manipur, India, since the beginning of the twentieth century. The tribal populations of Manipur are in the process of socioeconomic transition from a traditional subsistence economy to a market-oriented economy. The following table displays the relation between literacy level and subsistence group for a sam- ple of 614 married men and women in Manipur, India. DRY CAN .5 2.5 3.5 TYPE COST 3.0 2.0 1.5 1.0 DOG FOOD COSTS BY TYPE OF FOOD