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Bias is present in the following observational studies.

  1. Explain why the question in the following scenario is biased:

    A political pollster seeking information on public attitudes toward funding of pornographic art by the National Endowment for the Arts (NEA) asks a simple random sample of U.S. adults, “Instead of supporting government censorship of artistic expression, are you in favor of continuing federal funding for artists whose work may be controversial?” Eight-five percent of those surveyed answered “yes.”

  2. Explain why the sample in the following scenario is biased:

    A flour company in Minneapolis wants to know what percentage of local households bake at least twice a week. A company representative calls households during the daytime and finds that % of them bake at least twice a week.

    People at home during the day are more likely to have time to bake than the general population.

  3. Identify a possible lurking variable in the following scenario:

    Dentists would like to determine if eating an apple a day keeps cavities away. Fifty patients who say they routinely eat an apple a day, and patients who say they eat less than one apple a week, will have their dental records checked. The dentists will compare the number of cavities in the two groups.