The Excite Poll is an online poll at poll.excite.com. You click on an answer to

Question

The Excite Poll is an online poll at poll.excite.com. You click on an answer to become part of the sample. One poll question was "Do you prefer watching first-run movies at a movie theater, or waiting until they are available on home video or pay-per-view?" A total of 8896 people responded with 1118 saying they preferred theaters. From this survey, you should conclude that: A. Americans prefer watching movies at home. B. the poll uses voluntary response, so the results tell us little about the population of all adults. C. movie theaters should lower their prices. D. a larger sample is necessary. Sickle-cell disease is a painful disorder of the red blood cells that in the United States affects mostly African Americans. To investigate whether the drug hydroxyurea can reduce the pain associated with sickle-cell disease, a study by the NIH gave the drug to 150 sickle-cell sufferers and placebo to another 150. Neither doctors nor patients were told who received the drug. The number of episodes of pain reported by each subject was recorded. This is an example of a(n): A. double-blind experiment. B. paired data experiment. C. experiment, but not a double-blind experiment. D. observational study.

Explanation / Answer

Question 28:
Answer: B. The poll uses voluntary response, so the results tell us little about the population of all adults.

Voluntary bias occurs when the members select themselves to take part in the survey. They choose to take part only because they have strong feelings about the subject and overall this sample is not representative of all Americans.

Question 29:
Answer: A. double blind experiment

Since different group of people are involved in the treatment and placebo, the data is not paired. Since neither the doctors nor patients were aware of who received which drug, this is a double blind experiment.

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