Instructor Guide 2D: Forming Connections

Overview

  • This in-class activity should help students synthesize the ideas about experimental and observational studies learned in the previous two activities.
  • Students will examine a recent study from the Centers for Disease Control from which they were asked during the What to Know preview assignment to identify the who was studied and what data was observed for each participant.
  • This activity connects back to experimental design and forward to the optional advanced experimental design activity in Forming Connections [2E].
  • S2, S4, C2, C4, C5, C6, V1, V4, O1, O3 ← Link to EBTP descriptions 

Prerequisite assumptions

Students should be able to do each of the following after completing the What to Know assignment.

  • Identify an observational study.
  • Understand why observational studies are used.
  • Identify a confounding variable in an observational study.
  • Identify the difference between an experimental study and an observational study.

Intended goals for this activity

After completing this activity, students should understand that observational studies are different from experimental studies and that confounding factors can create associations in observational studies in ways that shouldn’t occur in controlled experiments with random assignment. They should be able to Identify an observational study, distinguish between experimental and observational studies, and identify possible confounding factors that might explain an apparent association.

Synchronous Delivery and Activity Flow

The sample activity delivery below assumes a face-to-face class meeting but can be adapted to a fully online or hybrid delivery by using break-out rooms for pairs and small groups.

Frame the activity (3 minutes)

  • Question1  — working in pairs S2, C4, V1, V4, O3
    • Have students discuss Question 1 for approximately three minutes. 
    • Have a few pairs share their answers to Question 1.
    • If necessary, prompt students to reflect on how smoking habits relate to depression in the example from the preview assignment: “What was being studied in the preview assignment? Why couldn’t, or shouldn’t, that be done via experimental design?”
    • Emphasize the necessity of observational studies in some circumstances due to ethical issues or the nature of the research question.
  • Transition to the in-class activity by briefly discussing the Objectives for the activity.

Activity Flow (18 minutes)

  • Question 2 – 6 — working in groups S2, V1, V4, C5, C6, O1, O3, S4 
    • “What makes an observational study different than an experimental study?”
    • “Did researchers assign a treatment to the participants?”
    • In Question 3, prompts include (if necessary):
      • “What else may influence someone’s positive COVID-19 diagnosis?”
      • “How reliable are COVID-19 tests?”
      • “What constitutes a confounding variable?”
    • Hold a brief discussion about Questions 2 – 4 before continuing. Keep two lists as a visual aid for the students: one list consists of the qualities of experimental studies, and the other list consists of the qualities of observational studies.
    • In Questions 5 and 6, remind students of the definition of a confounding variable, if necessary. Ask them:
      • “Can you think of another way to link higher reading scores with bigger feet?”
      • “Why else might residents of low-density rural areas suffer from fatal cancer diagnoses?”
      • Emphasize that experimental studies have treatments, random assignment of participants, cause-and-effect relationships, and “control.”
      • Emphasize observational studies not having different treatments, not having randomization of participants to treatments, and having a lack of control/presence of confounding variables.
      • Have groups share their answers to Questions 5 and 6.

Wrap-up/transition (5 minutes)

  • Encourage students to keep a list that compares experimental studies vs. observational studies.
  • Encourage students to further brainstorm why each type of study is necessary.
  • Have students refer back to the Objectives for the activity and check the ones they recognize. Alternatively, they may check the objectives throughout the activity.
  • If you will be working on optional In-Class Activity 2.E, transition by mentioning that the next activity involves the idea of advanced experimental design.
  • If you are going to In-Class Activity 3.A, transition by mentioning that as a class, students will be exploring student sleeping habits.
  • Assign the homework or Practice and any What to Know pages for the Forming Connections activities you plan to complete in the next class meeting. C2