(p. 79). One indicator of biodegradation is the level of dioxide in the water. Recall that 16 water specimens were randomly selected from various locations in a reservoir on the floor of a mine and the amount of dioxide (milligrams/liter) as well as presence of oil was determined for each specimen. These data are reproduced in the next table.

a. Estimate the true mean amount of dioxide present in water specimens that contain oil using a 95% confidence interval. Give a practical interpretation of the interval.

b. Repeat part a for water specimens that do not contain oil.

c. Based on the results, parts a and

b, make an inference about biodegradation at the mine reservoir. Dioxide Amount Crude Oil Present