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Chapter 4: Q 5. (page 226)

Call the shots A newspaper advertisement for an upcoming TV show said: “Should handgun control be tougher? You call the shots in a special call-in

poll tonight. If yes, call 1-900-720-6181If not, call 1-900-720-6182A charge is 50 cents for the first minute.” Explain why this opinion poll is almost certainly biased.

Short Answer

Expert verified

This opinion poll is almost certainly biased because it uses data from a voluntary response sample.

Step by step solution

01

Given information

An upcoming TV show's commercial asked: Should there be stricter gun laws? We need to explain why this opinion poll is almost probably biased, given over 90% of those that called in voting yes.

02

Concept

A simple random sample (SRS) of size n is made up of n people chosen from the population with an equal chance of being the sample that is actually chosen.

03

Explanation

Based on the television episode, a newspaper advertisement for the United States is shown: "Should handgun laws be strengthened? Because it draws data from a volunteer response sample, this opinion poll is almost probably skewed. It is made up of numerous people who choose themselves based on the voluntary response sample to the broad appeal. Almost never do voluntary response samples fully reflect the total population. They tend to overrepresent persons with strong beliefs since they are more likely to reply willingly to such polls.

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Most popular questions from this chapter

The ABC program Nightline once asked whether the United Nations should continue to have its headquarters in the United States. Viewers were invited to call one telephone number to respond “Yes” and another for “No.” There was a charge for calling either number. More than 186,000 callers responded, and 67% said “No.”

Is yawning contagious?According to the popular TV show Mythbusters, the answer is “Yes.” In the March 9,2005, episode, the Mythbusters team presented the results of an experiment involving 50subjects. All the subjects were placed in a booth for an extended period of time and monitored by hidden camera. Two-thirds of the subjects were given a “yawn seed” by one of the experimenters; that is, the experimenter yawned in the subject’s presence prior to leaving the room. The remaining subjects were given no yawn seed. What were the results? Of the 16subjects who had no yawn seed, 4 yawned. Of the 34 subjects given a yawn seed, 10 yawned. Adam Savage and Jamie Hyneman, the cohosts of Mythbusters, used these results to conclude that yawning is contagious.

(a) Explain how you could use slips of paper to randomly reassign the subjects to the treatment groups.

(b) Suppose we used your method in (a) to redo the random assignment 50 times. The Fathom dotplot displays the number of subjects in the yawn seed who yawned in each of these random assignments. What conclusion would you draw about whether yawning is contagious? Explain.

More rain for California? The changing climate will probably bring more rain to California, but we don’t know whether the additional rain will come during the

winter wet season or extend into the long dry season in spring and summer. Kenwyn Suttle of the University of California at Berkeley and his coworkers carried

out an experiment to study the effects of more rain in either season. They randomly assigned plots of open grassland to three treatments: added water equal to 20%of annual rainfall either during January to March (winter) or during April to June (spring), and no added water (control). Thirty-six circular plots of area 70square meters were available (see the photo), of which 18were used for this study. One response variable was total plant biomass, in grams per square meter, produced in a plot over a year.

(a) Outline the design of the experiment. What is this type of design called?

(b) Explain how you would randomly assign the experimental units to the three treatments. Then carry out your random assignment.

Cocoa and blood flowA study conducted by Norman Hollenberg, professor of medicine at Brigham and Women’s Hospital and Harvard Medical School,

involved 27healthy people aged 18-72. Each subject consumed a cocoa beverage containing 900milligrams of flavonols (a class of flavonoids) daily

for five days. Using a finger cuff, blood flow was measured on the first and fifth days of the study. After five days, researchers measured what they called “signifi-

cant improvement” in blood flow and the function of the cells that line the blood vessels. What flaw in the design of this experiment makes it impossible to say

whether the cocoa really caused the improved blood flow? Explain.

Sampling gravestones The local genealogical society in Coles County, Illinois, has compiled records on all 55,914 gravestones in cemeteries in the county from the years 1825 to 1985 Historians plan to use these records to learn about African Americans in Coles County’s history. They first choose an SRS of 395 records to check their accuracy by visiting the actual gravestones.13

(a) Explain how you would use technology or Table D to choose the SRS. Your description should be clear enough for a classmate to obtain your results.

(b) Use your method from (a) to choose the first 3 gravestones.
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