After a heavy storm, the waste water holding tanks at a waste water treatment pl

Question

After a heavy storm, the waste water holding tanks at a waste water treatment plant on the New River overflowed dumping 1,000,000 gallons of sewage into the New River. You are part ofthe New River Citizen Watch Group, which monitors the health of portions of the New River for government agencies like the EPA and USDA. This sewage discharge event causes your group to wonder if the event has had a negative impact on the quality of the water downstream of the waste water treatment plant. To test your group's idea that the sewage has negatively impacted water quality, you measure in triplicate the EPT of a site upstream of the waste water treatment plant and a site downstream of the waste water treatment plant. You calculate the mean 9% EPT of both sites and the 95% confidence intervals of both samples. Your results are shown below. Use this scenario and data to answer the following questions. 120 1000 60 Upstream site Downstream site

Explanation / Answer

Ans. 1. Independent variables: The variable that acts as the factor/ inputs, etc. presenting the cause of variation in outputs. Since data is being collected from both upstream and downstream site- the factor responsible for variation in output (% mean EPT)- both the sites are independent variable.

Correct option- D. the collection sites

Ans. 2. Dependent variable: A ‘variation’ that depends on the independent variable for the its change is called dependent variable.

For example, in the given example, the upstream and downstream sites are independent variable, i.e. the factor that present variation in the outputs (% mean EPT).

So, measuring % EPT is a dependent variable.

Correct option: C. Measuring % EPT.

Ans. 3. Note the statement- “—to wonder if the event has had a negative impact on the quality of the water downstream of the waste water treatment plant”.

To test the idea, the % mean EPT of the downstream site is compared with that of upstream site. Here, the upstream site serves as control (or reference) group- that is, the result of downstream is to be compared with the upstream for testing the “idea”. The downstream group, which is being compared with the control group (upstream site) serves as the experimental group- the group which is expected to show variation from the upstream site due to sewage mixing.

Thus, downstream site is the experimental group here.

Correct option: F. Downstream site.

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