For Exercise 1.1, see page 11; for Exercise 1.2, see page 13.
1.3 Individuals and variables. A national survey by the Pew Research Center and USA Today, conducted August 20–24, 2014, was based on telephone interviews among a national sample of 1501 adults, 18 years of age or older, living in all 50 U.S. states and the District of Columbia. Those interviewed were asked to rate the job performance of police forces across the country for holding officers accountable when misconduct occurs. Possible ratings were “Excellent,” “Good,” “Only fair,” and “Poor.” Seventy percent of black respondents gave a rating of “Poor,” while only 27% of white respondents gave a rating of “Poor.” For this study,
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(a) the individuals are the sample of 1501 adults interviewed.
(b) the variable is the rating a respondent selected.
(c) both (a) and (b).
(d) neither (a) nor (b).
1.4 Population and sample. For the survey described in the previous exercise,
(a) the population is the 1501 adults interviewed and the sample are those who gave a rating of poor.
(b) the population is all adults, 18 years of age or older, living in all 50 U.S. states and the District of Columbia, and the sample are those who gave a rating of poor.
(c) the population is all adults, 18 years of age or older, living in all 50 U.S. states and the District of Columbia, and the sample is the black and white respondents.
(d) the population is all adults, 18 years of age or older, living in all 50 U.S. states and the District of Columbia, and the sample is the 1501 adults interviewed.
1.5 Observational studies and experiments. Researchers at The Ohio State University studied the effect of acetaminophen on emotion. The study included a total of 167 volunteers. Approximately half were randomly assigned to take acetaminophen and the other half a placebo. All subjects were shown a variety of images intended to invoke emotions. “Whether they saw things likely to make them feel bad or make them feel good, the acetaminophen group had a less-intense response. It’s not that they didn’t feel sad or happy, just that they felt less (by about 10 to 20%) than their placebo-swallowing peers. It doesn’t turn them into zombies. It doesn’t turn them into robots,” one of the researchers said. Which of the following is true?
(a) This is an observational study, and participants were volunteers.
(b) This is an observational study, and participants were selected at random.
(c) This is an experiment, but participants themselves decided whether to take acetaminophen or the placebo.
(d) This is an experiment, and participants were randomly assigned to treatments.
1.6 Response variable. For the study described in the previous exercise, the response variable is which of the following?
(a) Some measure of emotional intensity invoked by the images
(b) Whether a subject received acetaminophen or the placebo
(c) The images
(d) The 167 volunteers
1.7 A census? A study is considered to be a census if
(a) the population of interest is very large.
(b) the study attempts to measure every individual in a population.
(c) all units in the study receive some treatment.
(d) it attempts to answer questions about the opinions of all citizens of a particular country.