Refer to the Journal of Petroleum Geology (April 2010) study of the environmental factors associated with biodegradation in crude oil reservoirs, Exercise 6.38. Recall that 16 water specimens were randomly selected from various locations in a reservoir on the floor of a mine and that the amount of dioxide (milligrams/liter)-a measure of biodegradation-as well as presence of oil were determined for each specimen. These data are reproduced in the accompanying table.

a. Conduct a test to determine if the true mean amount of dioxide present in water specimens that contained oil was less than 3 milligrams/liter. Use α = .10.

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

Dioxide Amount Crude Oil Present

3.3.............................................................No

0.5.............................................................Yes

1.3.............................................................Yes

0.4.............................................................Yes

0.1.............................................................No

4.0.............................................................No

0.3.............................................................No

0.2.............................................................Yes

2.4.............................................................No

2.4.............................................................No

1.4.............................................................No

0.5.............................................................Yes

0.2.............................................................Yes

4.0.............................................................No

4.0.............................................................No

4.0.............................................................No