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Chapter 4: Q. 7 (page 236)

Online reviews Many websites include customer reviews of products, restaurants, hotels,

and so on. The manager of a hotel was upset to see that 26%of reviewers on a travel

website gave the hotel “1star”—the lowest possible rating. Explain how bias in the

sampling method could affect the estimate.

Short Answer

Expert verified

The answer is a voluntary response sample.The subjects themselves can determine whether or not they are in the sample. We will only have data about the strongest opinions

Step by step solution

01

Given information

We have to find the bias in the sampling method.

02

Explanation

The sample in the exercise prompt is a text voluntary response sample because the subjects must willingly answer the online poll (you can view the online poll without answering it), and so the subjects themselves can determine whether or not they are in the sample.Because people with the strongest opinions choose to engage in a voluntary response sample, we will only have data about the strongest opinions, resulting in us continuously overestimating or underestimating the actual opinions.

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Most popular questions from this chapter

A local news agency conducted a survey about unemployment by randomly dialing phone

numbers during the work day until it gathered responses from 1000 adults in its state. In

the survey, 19% of those who responded said they were not currently employed. In reality,

only 6% of the adults in the state were not currently employed at the time of the survey.

Which of the following best explains the difference in the two percentages?

a. The difference is due to sampling variability. We shouldn’t expect the results of a

random sample to match the truth about the population every time.

b. The difference is due to response bias. Adults who are employed are likely to lie and

say that they are unemployed.

c. The difference is due to undercoverage bias. The survey included only adults and did

not include teenagers who are eligible to work.

d. The difference is due to nonresponse bias. Adults who are employed are less likely to

be available for the sample than adults who are unemployed.

e. The difference is due to voluntary response. Adults are able to volunteer as a member

of the sample.

A report in a medical journal notes that the risk of developing Alzheimer’s disease among subjects who regularly opted to take the drug ibuprofen was about half the risk of those who did not. Is this good evidence that ibuprofen is effective in preventing Alzheimer’s disease?

a. Yes, because the study was a randomized, comparative experiment.

b. No, because the effect of ibuprofen is confounded with the placebo effect.

c. Yes, because the results were published in a reputable professional journal.

d. No, because this is an observational study. An experiment would be needed to confirm

(or not confirm) the observed effect.

e. Yes, because a 50%reduction can’t happen just by chance.

Side effects Even if an experiment is double-blind, the blinding might be compromised if side effects of the treatments differ. For example, suppose researchers at a skin-care company are comparing their new acne treatment against that of the leading competitor. Fifty subjects are assigned at random to each treatment, and the company’s researchers will rate the improvement for each of the 100subjects. The researchers aren’t told which subjects received which treatments, but they know that their new acne treatment causes a slight reddening of the skin. How might this knowledge compromise the blinding? Explain why this is an important consideration in the experiment.

Seat belt use A study in El Paso, Texas, looked at seat belt use by drivers. Drivers were

observed at randomly chosen convenience stores. After they left their cars, they were

invited to answer questions that included questions about seat belt use. In all, 75% said

they always used seat belts, yet only 61.5% were wearing seat belts when they pulled into

the store parking lots. Explain why the two percentages are so different.

Your statistics class has 30students. You want to ask an SRS of 5students from your class whether they use a mobile device for the online quizzes. 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

b. 14,31,03,10,22

c. 14,03,10,22,22

d.14,03,10,22,06

e.14,03,10,22,11
See all solutions

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