Chapter 1.3, Problem 4E

Following are measurements of soil concentrations (in mg/kg) of chromium (Cr) and nickel (Ni) at 20 sites in the area of Cleveland, Ohio. These data are taken from the article “Variation in North American Regulatory Guidance for Heavy Metal Surface Soil Contamination at Commercial and Industrial Sites” (A. Jennings and J. Ma, J Environment Eng, 2007:587–609).

Cr:    34    1    511    2    574    496    322    424

269    140    244    252    76    108    24    38

18    34    30    191

Ni:    23    22    55    39    283    34    159    37

61    34    163    140    32    23    54    837

64    354    376    471

1. a. Construct a histogram for each set of concentrations.
2. b. Construct comparative boxplots for the two sets of concentrations.
3. c. Using the boxplots, what differences can be seen between the two sets of concentrations?