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  Module 2
  Module 3
  Module 4
  Module 5

Investigation 2-4
Backpacks and Back Pain


Students test the hypothesis that carrying a heavy backpack causes back pain.  Using a 2x2 table, students perform an in-class observational study by collecting and analyzing data from the "natural experiment" that they perform on themselves by carrying their backpacks.  This first-hand experience in conducting an observational study helps students understand procedures involved in creating definitions of an exposure and an outcome, displaying data in a 2x2 table, calculating risks, comparing risks (calculating relative risk), and making inferences.

Investigation Preparation Checklist

Check alignment with standards.

National or State file

Review Epidemiology Background for Module 2.

Word or PDF file

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

  • Not animated.  Recommended for quick viewing.
  • PDF: 983KB

  • Not animated.  Recommended for printing.
  • Word: 3,171KB

  • Animated viewing with Microsoft Internet Explorer.
  • HTML Web file: 4,770KB

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  • PowerPoint file: 4,098KB

    Copy Investigation 2-4: Epi Log Worksheet for each
    student.  [en espaņol:]

    Word or PDF file

    Copy Investigation 2-4: 2x2 Table Sheet for each student.  [en espaņol:]

    Word or PDF file

    Copy article, "Backpack May Spell Back Ache," for each
    student and assign to be read prior to the next class.

    Word or PDF file

    Remind students to bring their backpacks to class.


    Bring scales to class.


    Estimated Time / Time Management

    Approximately one class period. Time can be managed by having students read "Backpack May Spell Back Ache" for homework prior to the investigation.

    Look For Students To:

    Describe the procedure for conducting an observational study including formulating a hypothesis, defining exposure and outcome, identifying a sample, and informed consent.

    Accurately display observational data in a 2x2 table.

    Carry out the study in a way that shows "respect for persons."

    Accurately calculate risks and relative risk.

    Given the hypothesis, make logical inferences from their data.