Refer to the Chemical Engineering Journal (April, 2013) study of a method for removing nitrogen from toxic wastewater, Exercise 10.53. Recall that the researchers related y = the amount of nitrogen removed (measured in milligrams per liter) from a wastewater specimen to x = the amount of ammonium (milligrams per liter) used in the removal process using data collected for 120 specimens. The data for the first 5 specimens are shown below.

a. Using only the data for the first 5 specimens, find Spearman’s rank correlation between y and x.

b. Based on the result, part a is the amount of nitrogen removed significantly positively correlated with amount of ammonium? Test using α = .01.

c. Repeat parts a and b, using the full sample of 120 wastewater specimens.

Data from Exercise 10.53

Highly toxic wastewater is produced during the manufacturing of dry spun acrylic fiber. One way to lessen toxicity is to remove the nitrogen from the wastewater. A group of environmental engineers investigated a promising method—called anaerobic ammonium oxidation—for nitrogen removal and reported the results in the Chemical Engineering Journal (April 2013). A sample of 120 specimens of toxic wastewater was collected and each treated with the nitrogen removal method. The amount of nitrogen removed (measured in milligrams per liter) was determined as well as the amount of ammonium (milligrams per liter) used in the removal process. These data (simulated from information provided in the journal article) are saved in the NITRO file.

Transcribed Image Text:

NITRO (First 5 observations of 120 shown) Nitrogen Ammonium 18.87 67.40 17.01 12.49 23.88 61.96 10.45 15.63 36.03 83.66