57. Living Below the Poverty Level. For the following survey, describe the target population and the potential population, and discuss the potential for selection bias. A sociologist is interested in the proportion of people living below the poverty level in Chicago. He takes a random sample of phone numbers from the Chicago phone directory and asks each respondent his or her annual household income.
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Target population: all the people living in Chicago; potential population: people who have phones and who have their phone number listed in the Chicago phone directory. Reasons for potential selection bias vary; for instance, many of the people living below the poverty level in Chicago may not have phones.