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Chapter 4: Q 1.2. (page 233)

Does eating dinner with their families improve students’ academic performance? According to an ABC News article, “Teenagers who eat with their families at least five times a week are more likely to get better grades in

school.”19 This finding was based on a sample survey conducted by researchers at Columbia University.

Was this an observational study or an experiment? Justify your answer.

Short Answer

Expert verified

Experimental Study.

Step by step solution

01

Given information

Teenagers who eat with their family at least five times per week are more likely to excel academically.

02

Concept

Observational research looks at people and assesses factors of interest without trying to affect their responses.

Individuals are purposely subjected to a treatment in order to measure their responses in an experiment.

03

Explanation

This is an experimental study in which both the test and control groups are tested and kept in a controlled environment with adequate variable modifications according to needs.

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Most popular questions from this chapter

an SRS of 5 students from your class to ask where they use a computer for the online exercises. You label the students 01,02,...,30 You enter the table

of random digits at this line:

1445926056314248037165103622532249061181

Your SRS contains the students labeled

(a)14,45,92,60,56.(d)14,03,10,22,06.(b)14,31,03,10,22.(e)14,03,10,22,11.(c)14,03,10,22,22.

Chocolate gets my heart pumping Cardiologists at Athens Medical School in Greece wanted to test whether chocolate affected blood flow in the blood vessels. The researchers recruited 17healthy young volunteers, who were each given a 3.5-ounce bar of dark chocolate, either bittersweet or fake chocolate.

On another day, the volunteers were switched. The subjects had no chocolate outside the study, and investigators didn’t know whether a subject had eaten the real or the fake chocolate. An ultrasound was taken of each volunteer’s upper arm to see the functioning of the cells in the walls of the main artery. The investigators found that blood vessel function was improved when the subjects ate bittersweet chocolate, and that there were no such changes when they ate the placebo (fake chocolate).

(a) What type of design did the investigators use in their study?

(b) Explain why the investigators chose this design instead of a completely randomized design.

(c) Why is it important to randomly assign the order of the treatments for the subjects?

Effects of binge drinking A common definition of “binge drinking” is 5 or more drinks at one sitting for men and 4 or more for women. An observational study

finds that students who binge drink have lower average GPA than those who don’t. Identify a lurking variable that may be confounded with the effects of binge drinking. Explain how confounding might occur.

Learning biology with computers An educator wants to compare the effectiveness of computer software for teaching biology with that of a textbook presentation. She gives a biology pretest to each group of high school juniors, then randomly divides them into two groups. One group uses the computer, and the other studies the text. At the end of the year, she tests all the students again and compares the increase in biology test scores in the two groups.

(a) Is this an observational study or an experiment? Justify your answer.

(b) If the group using the computer has a much higher average increase in test scores than the group using the textbook, what conclusions if any, could the educator draw?

Customer satisfaction A department store mails a customer satisfaction survey to people who make credit card purchases at the store. This month, 45,000

people made credit card purchases. Surveys are mailed to 1000 of these people, chosen at random, and 137 people return the survey form. Identify the

population and the sample.
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