The 2009 National Survey on Drug Use and Health selected a random sample of U.S. college students and asked them about possible illicit drug use. Approximately 23% of the students surveyed reported using illicit drugs in the past year. The sample in this study is:
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U.S. college students.
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the 23% of the students who reported using illicit drugs.
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the college students who responded to the National Survey on Drug Use and Health.
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all U.S. adults.