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Chapter 4: Q AP1.3. (page 276)
A large set of test scores has a mean and a standard deviation of If each score is doubled, and then is subtracted from the result, the mean and standard deviation of the new scores are
The correct option is (b)
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The Web portal AOL places opinion poll questions next to many of its news stories. Simply click your response to join the sample. One of the questions
in January was 鈥淒o you plan to diet this year?鈥� More than people responded, with saying 鈥淵es.鈥� You can conclude that
(a) about of Americans planned to diet in
(b) the poll used a convenience sample, so the results tell us little about the population of all adults.
(c) the poll uses voluntary response, so the results tell us little about the population of all adults.
(d) the sample is too small to draw any conclusion.
(e) None of these.
Cocoa and blood flowA study conducted by Norman Hollenberg, professor of medicine at Brigham and Women鈥檚 Hospital and Harvard Medical School,
involved healthy people aged . Each subject consumed a cocoa beverage containing milligrams 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 鈥渟ignifi-
cant improvement鈥� 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.
Explain it to the congresswoman You are on the staff of a member of Congress who is considering a bill that would provide government-sponsored insurance for nursing-home care. You report that letters have been received on the issue, of which oppose the legislation. 鈥淚鈥檓 surprised that most of my constituents oppose the bill. I thought it would be quite popular,鈥� says the congresswoman. Are you convinced that a majority of the voters oppose the bill? How would you explain the statistical issue to the congresswoman?
Killing weeds A biologist would like to determine which of two brands of weed killer is less likely to harm the plants in a garden at the university. Before spraying near the plants, the biologist decides to conduct an experiment using 24 individual plants. Which of the following two plans for randomly assigning the treatments should the biologist use? Why?
Plan A: Choose the healthiest-looking plants.
Apply Brand X weed killer to all of those plants.
Apply Brand Y weed killer to the remaining plants.
Plan B: Choose of the plants at random. Apply
Brand X weed killer to those plants and Brand Y
weed killer to the remaining plants.
Improving response rate How can we reduce the rate of refusals in telephone surveys? Most people who answer at all listen to the interviewer鈥檚 introductory remarks and then decide whether to continue. One study made telephone calls to randomly selected households to ask for opinions about the next election. In some calls, the interviewer gave her name, in others she identified the university she was representing, and in still others, she identified both herself and the university. For each type of call, the interviewer either did or did not offer to send a copy of the final survey results to the person interviewed. Do these differences in the introduction affect whether the interview is completed?
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