Chapter 5.12, Problem 41E

The amount of sewage and industrial pollutants dumped into a body of water affects the health of the water by reducing the amount of dissolved oxygen available for aquatic life. Over a 2-month period, eight samples were taken from a river at a location 1 mile downstream from a sewage treatment plant. The amount of dissolved oxygen in the samples was determined and is reported in the following table. The current research asserts that the mean dissolved oxygen level must be at least 5.0 parts per million (ppm) for fish to survive.

1. a. Place a 95% confidence on the mean dissolved oxygen level during the 2-month period.
2. b. Using the confidence interval from part (a), does the mean oxygen level appear to be less than 5 ppm?
3. c. Test the research hypothesis that the mean oxygen level is less than 5 ppm. What is the level of significance of your test? Interpret your findings.