Environmental Engineering An article in the Journal of the Environmental Engineering Division ("Distribution of Toxic Substances in Rivers," Vol 108, 1982 pp.639-649) describes a study of the concentration of several hydrophobic organic substances in the Wolf River in Tennessee. Measurements of hexachlorobenzene (HCB) in nanograms per liter were taken at different depths downstream of an abandoned dump site. Data for two depths are as follows: Surface: 3.74, 4.61, 4.00, 4.67, 4.87, 5.12, 4.52, 5.29, 5.74, 5.48, 5.10, 4.95 Bottom: 5.44, 6.88, 5.37, 5.44, 5.03, 6.48, 3.89, 5.85, 6.85, 7.16, 5.70, 4.50 Directions: Answer the questions and complete the following exercise. 1. What is the goal of this study? 2. Define the main variable. 3. What constitutes the population of this study? What is the sample size? 4. Compute the mean, median, and standard deviation of each data set