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Chapter 7: Q. 22 (page 464)

AP2.22. A health worker is interested in determining if omega-3fish oil can help reduce cholesterol in adults. She obtains permission to examine the health records of200 people in a large medical clinic and classifies them
according to whether or not they take omega-3fish oil. She also obtains their latest cholesterol readings and finds that the mean cholesterol reading for those who are taking omega-3fish oil is 18points lower than the mean for the group not taking omega-3 fish oil.
(a) Is this an observational study or an experiment? Explain.
(b) Do these results provide convincing evidence that taking omega-3 fish oil lowers cholesterol?
(c) Explain the concept of confounding in the context of this study and give one example of a possible confounding variable.

Short Answer

Expert verified

(a) The study is observational.

(b) The results do not provide convincing evidence that taking omega- 3fish oil lowers cholesterol.

(c) Two variables are confounded when their effects on a response variable cannot be distinguished. One example for possible confounding variable is the amount of exercise.

Step by step solution

01

Part (a) Step 1: Given information

The health records of 200people in a large medical clinic and classifies, according to whether or not they take omega -3fish oil. To explain the observational study or an experiment.

02

Part (a) Step 2: Explanation

In the given data, an experiment gradually sets some treatments on people to monitor their comebacks. An observational analysis attempts to collect data without bothering the scene.
No treatments were allocated to the 200people as the information is founded on health records and the researchers didn't include any control over who took the omega-3fish oil and who didn't. As no treatments were given.

Hence, the study is observational.

03

Part (b) Step 1: Given information

The mean cholesterol reading for those who are taking omega-3fish oil is 18points lower than the mean for the group not taking omega-3fish oil. To explain those results provide evidence that taking omega-3 fish oil lowers cholesterol.

04

Part (b) Step 2: Explanation 

A health worker is experimenting with discovering if omega- 3fish oil can help reduce cholesterol levels in adults or not. As no treatments were assigned the study is observational.

Since there are possible confounding variables we cannot be 100%sure that the omega- 3fish oil is the cause of the statistically significant difference can be other factors influencing the outcome.

Hence, these results do not provide convincing evidence that taking omega- 3 fish oil lowers cholesterol.

05

Part (c) Step 1: Given information

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

06

Part (c) Step 2: Explanation

In this study, two variables are confounded when their effects on a response variable cannot be distinguished from each other. People who take omega-3fish oil might be more curious in maintaining good health and these people might exercise more.

The amount of exercise also affects our cholesterol levels and cannot distinguish the effects of the amount of exercise from the omega-3-fish oil, which indicates that the portion of exercise is confounded with the omega-3 fish oil.
Hence, two variables are confounded when their effects on a response variable cannot be distinguished from each other.

One example for possible confounding variable is the amount of exercise.

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Most popular questions from this chapter

Doing homework Refer to Exercise 9.

(a) Make a graph of the population distribution given that there are 3000 students in the school. (Hint: What type of variable is being measured?)

(b) Sketch a possible graph of the distribution of sample data for the SRS of size 100 taken by the AP Statistics students.

identify the population, the parameter, the sample, and the statistic in each setting

Unemployment Each month, the Current Population Survey interviews a random sample of individuals in about 55,000U.S. households. One of their goals is to estimate the national unemployment rate. In December 2009,10.0%of those interviewed were unemployed

Do you jog? The Gallup Poll once asked a random sample of1540adults, "Do you happen to jog?" Suppose that in fact 15%of all adults jog.

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(c) Is the sampling distribution of p^approximately Normal? Justify your answer.

(d) Find the probability that between 13%and 17%of a random sample of 1540adults are joggers. Show your work.

Your mail-order company advertises that it ships 90%of its orders within three working days. You select an SRS of 100of the 5000orders received in the past week for an audit. The audit reveals that 86of these orders were shipped on time.

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(b) A critic says, 鈥淎ha! You claim 90%, but in your sample, the on-time percentage is lower than that. So the 90%claim is wrong.鈥� Explain in simple language why your probability calculation in (a) shows that the result of the sample does not refute the 90%claim.

Increasing the sample size of an opinion poll will

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