Chapter 7, Problem 22PT2

(a)

To determine

To explain is this an observational study or an experiment.

Answer to Problem 22PT2

The study is an observational study.

Explanation of Solution

It is given in the question, a health worker is interested in finding if omega- $3$ fish oil can help reduce cholesterol level in adults or not. Thus, as we know that an experiment deliberately imposes some treatment on individuals in order to observe their responses. And an observational study tries to gather information without disturbing the scene they are observing. Thus, no treatments were assigned to the subjects as the data is based on health records and thus the researchers did not have any control over who took the omega- $3$ fish oil and who did not. As no treatments were assigned the study is an observational study.

(b)

To determine

To explain do these results provide convincing evidence that taking omega- $3$ fish oil lowers cholesterol.

Answer to Problem 22PT2

These results do not provide convincing evidence that taking omega- $3$ fish oil lowers cholesterol.

Explanation of Solution

It is given in the question, a health worker is interested in finding if omega- $3$ fish oil can help reduce cholesterol level in adults or not. As no treatments were assigned the study is an observational study. And that the study had possible confounding variables. Since there are possible confounding variables we cannot be $100\%$ sure that the omega- $3$ fish oil is the cause of the statistically significant difference as there can be other factors affecting the result. Therefore, these results do not provide convincing evidence that taking omega- $3$ fish oil lowers cholesterol.

(c)

To determine

To explain the concept of confounding in the context of this study and given one example of a possible confounding variable.

Explanation of Solution

It is given in the question, a health worker is interested in finding if omega- $3$ fish oil can help reduce cholesterol level in adults or not. As no treatments were assigned the study is an observational study. And that the study had possible confounding variables. As we know that, two variables are confounded when their effects on a response variable cannot be distinguished from each other. Thus, people who take omega- $3$ fish oil might be more interested in having a good health and thus these people might exercise more. However, the amount of exercise also affects our cholesterol levels and thus we cannot distinguish the effects of the amount of exercise from the omega- $3$ fish oil, which means that the amount of exercise is confounded with the omega- $3$ fish oil.