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Investigation 3-6
Selection Bias


Students explore the fifth of five possible explanations for finding an association: bias.  Students critique a hypothetical study testing the hypothesis that heavy backpacks cause back pain and learn how the selection of a sample of subjects for a study can produce an association when no association exists in the overall population.  They continue to learn that causation is only one explanation for finding an association between an exposure and an outcome; that because observational studies are flawed, other explanations must also be considered, including selection bias.

Investigation Preparation Checklist

Check alignment with standards.

National or State file

Review Epidemiology Background for Module 3.

Word or PDF file

Review teacher's notes and slides:  [en espaņol:]

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    Copy Investigation 3-6: Epi Log Worksheet for
    each student.  [en espaņol:]

    Word or PDF file

    Estimated Time / Time Management

    Approximately one class period.

    Look For Students To:

    Appreciate that an association is found by making and comparing rates.

    Appreciate that association is not synonymous with causation.

    Consider explanations other than causality for an association.

    Describe a study design that found an association between an exposure and an outcome that could be due to selection bias.