Overview

• This in-class activity allows students to apply what they have learned about experimental design in the preview assignment to create their own hypothetical experiment.
• This builds on concepts already learned surrounding types of data and data collection, data interrogation, and sampling methods.
• This activity connects back to data collection and organization and asking good statistical questions, and connects forward to discussions about experimental vs. observational studies.
• S2, S4, C2, C4, C5, C6, V1, V4, 03 ← Link to EBTP descriptions 

Prerequisite assumptions

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

• Identify the factor of interest and response factor in an experiment.
• Identify the nuisance factors in an experiment.
• Identify the experimental and control groups in an experiment.
• Recognize random assignment.
• Identify which of two methods of replication was used in an experiment.

Intended goals for this activity

After completing this activity, students should understand that experimental design is a specific method of scientific inquiry, that experiments are useful in determining cause-and-effect relationships between variables, and that the three key mechanisms of experimental design are randomization, replication, and comparison. They should be able to identify key components of experimental design, including: treatment, factor of interest (also known as the explanatory variable or independent variable), response variable (also known as the dependent variable), nuisance factors, random assignment, and replication. They should be able to design a hypothetical experiment to answer a research question.

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 (5 minutes)

• Students will work in groups throughout this activity. The ideal group size is 3 to 4 students. S2, C4, V1, V4, O3
• Question 1 — in groups
  • Students brainstorm possible factors in their groups for one minute. Suggested prompts if needed:
    • “What do plants need to survive?”
    • “What do animals need to survive?”
    • “What are some characteristics of the ocean that have been changing in recent years?”
  • Each group shares their ideas with the class.
  • Keep a running list that is visible for the rest of the activity—students may find it helpful for Question 3, Part B.
• Transition to the in-class activity by briefly discussing the Objectives for the activity.

Activity Flow (15 minutes)

• Optional: Hand out the Experimental Design Worksheet if you would like students to use it to answer Questions 2– 4..
• Question 2 – 3 — working in groups C5, C6, V1, V4, O3, S4
  • Circulate through the classroom and check in with the groups. Provide guidance and redirection as needed. Key concepts to check:
    • Question 2: Does the research question contain a cause-and-effect relationship?
    • Question 3, Part A: Did the students accurately identify the factor of interest and response variable?
    • Question 3, Part B: Students should have a plan for an experimental and control group with a list of factors that will be kept the same between both groups. The control group should have the factor of interest set to a “baseline” level, while the experimental group should have the factor of interest set to a plausible experimental level. Students may need guidance regarding the measurement of the response factor.
    • Question 3, Part C: Students should have a plan to randomly assign groups. Students should consider sample size and be able to explain the benefits of replication. If students mention random sampling, remind them that it is not required for experimental design.
• Question 4 — Presentations V4, C6, S4
  • Have students share their answers to Question 4. Depending on class size and resources available, different strategies may be used. Emphasize concise communication of key points.
  • High-tech, small class: digital presentations (posters, flyers, wikis, webpages, etc.), each group displays for the whole class
  • High-tech, large class: digital presentations (posters, flyers, wikis, webpages, etc.), each group displays for 3 to 4 other groups
  • Low-tech, small class: paper-based presentations (posters, flyers, reports, etc.), each group shares with the whole class
  • Low-tech, large class: paper-based presentations (posters, flyers, reports, etc.), each group shares with 3 to 4 other groups

Wrap-up/transition (5 minutes)

• Allow students to view other groups’ work. Encourage comments on similarities and differences to their own work.
• If extra time is left in class, have students identify each component of another group’s experiment.
• 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.
• Prepare students to start thinking about other types of research.
• “Experimental design is useful in situations where the factor of interest can be manipulated by the researcher. Not all situations are like that though. Can you think of an example where a researcher might not be able to manipulate the factor of interest?”
  • Examples:
    • Does educational level affect income? (Can’t manipulate/randomly assign an education)
    • Do men or women have a higher risk of developing heart disease? (Can’t manipulate/assign sex)
    • Does smoking cause lung cancer? (Not ethical to randomly assign people to smoke)
• Let students know that, in the next activity, they will learn about observational studies through the context of vaccination.
• 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