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  Module 2
  Module 3
  Module 4
  Module 5

Investigation 2-2
Compared to What?


Students examine the need for a control group and have more experience in using a 2x2 table.  First, students learn how risks are calculated from the 2x2 table.  Students then compare the risks of disease among the exposed and unexposed groups of people.  This calculation is called a relative risk.  From the relative risk, students learn to make inferences based on the similarities or differences between two risks.

Students realize that a hypothesis can only be tested when risks of getting a disease are compared among exposed and unexposed groups.  They also learn the importance of calculating a relative risk by realizing that the same risk of getting a disease in the exposed group (for example, 10%) may lead to different inferences depending on the rate of disease in the unexposed group (10%, 1%, or 40%).

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:]

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  • PowerPoint file: 2,217KB

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

    Word or PDF file

    Copy Investigation 2-2: Homework for each student.

    Word or PDF file

    Review Investigation 2-2: Homework Answer Key.

    Word or PDF file

    Estimated Time / Time Management

    Approximately one class period.

    Look For Students To:

    Explain why a control group is needed.

    Calculate rates and relative risks.

    Make inferences based on the similarities or differences between rates.