15.8 Dissolved O Content The observations in the table are dissolved oxygen contents in water. The higher the dissolved oxygen content, the greater the ability of a river, lake, or stream to support aquatic life. In this experiment, a pollution-control inspector suspected that a river community was releasing semitreated sewage into a river. To check this theory, five randomly selected specimens of river water were selected at a location above the town and another five below. These are the dissolved oxygen readings (in parts per million):

a. Use a one-tailed Wilcoxon rank sum test with a=0.05 to confirm or refute the theory.

b. Use a Student's t test (with a = 0.05) to analyze the data. Compare the conclusion reached in part a.

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Above town Below town 4.8 5.2 5.0 4.9 5.1 5.0 4.7 4.9 4.8 4.9