Industrial wastes and sewage dumped into our rivers and streams absorb oxygen and thereby reduce the amount of dissolved oxygen available for fish and other forms of aquatic life. One state agency requires a minimum of 5 parts per million (ppm) of dissolved oxygen in order for the oxygen content to be sufficient to support aquatic life. 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.
Above Town | 4.7 | 5.3 | 5.0 | 4.8 | 5.1 |
---|---|---|---|---|---|
Below Town | 5.0 | 4.6 | 4.8 | 4.8 | 5.0 |
(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 α = 0.05. (Use μ_{1} for the population mean for the above town location and μ_{2} for the population mean for the below town location.)
State the test statistic. (Round your answer to three decimal
places.)
t =
State the rejection region. (If the test is one-tailed, enter NONE
for the unused region. Round your answers to three decimal
places.)
t > |
Suppose you prefer estimation as a method of inference. Estimate
the difference in the mean dissolved oxygen contents (in ppm) for
locations above and below the town. Use a 95% confidence interval.
(Use μ_{1} − μ_{2}. Round your answers to three
decimal places.)
ppm to ppm
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