20. Dissolved O2 Content A pollution control inspector suspected that a river community was releasing amounts of semitreated sewage into a river. To check his theory, he drew five randomly selected specimens of river water at a location above the town, and another five below. The dissolved oxygen readings (in parts per million) are as follows:

a. Do the data provide sufficient evidence to indicate that the mean oxygen content below the town is less than the mean oxygen content above? Test using a 5.05.

b. Estimate the difference in the mean dissolved oxygen contents for locations above and below the town.
Use a 95% confidence interval.

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