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Lesson 7: Observational Studies vs. Experiments

Lesson 7: Observational Studies vs. Experiments

Objective

You will learn how observational studies differ from experiments, and you will classify different research scenarios based on which method would be most appropriate. You will also learn about the roles of ethics, cost limitations, and feasibility when deciding between the two data collection methods.

Materials

  1. What Should We Do? handout (LMR_3.3_ObsStudies vs Experiments)

Vocabulary

ethics, cost limitations, feasibility

Essential Concepts

Essential Concepts

Experiments are not always possible because of various factors such as ethics, cost limitations, and feasibility.

Lesson

  1. Recall from the previous lesson that in observational studies, subjects are never randomly assigned to treatment and control groups. On the other hand, in experiments, random assignments are always made.

  2. Record your answer to the following question:

    Why can’t we always just do experiments?

  3. A researcher wants to perform studies to answer the research questions below. In your IDS Journal, write down reasons for why an experiment would not be possible for each scenario. Click and check your answers:


    Does smoking cause lung cancer? Unethical. You cannot make people smoke cigarettes and then see if they have lung cancer later in life.


    Does drinking water from Mars keep you healthier than drinking water from Earth? Cost. It would be incredibly expensive to design a space shuttle that can successfullytransport people to Mars and have them live there for an extended period of time, and most researchers would not have the funding to do this.


    Do people with higher IQ scores score better on the SAT than people with lower IQ scores? Not feasible/not possible. You cannot randomly assign IQ scores to people because it is a measurement based on aptitude.

  4. Select three teams and assign a scenario above to each team. Ask each team to report out on their assigned scenario. As teams share, be sure to discuss the following issues regarding why we cannot always to experiments:

    1. Ethics: Sometimes, experiments cannot be performed because it would be unethical to give certain treatments to subjects. For example, we could not inject an infectious disease into participants because the long-term effects might lead to death.

    2. Cost Limitations: Sometimes, experiments would be very costly and much too expensive to perform. Some possibilities could be with technology.

    3. Feasibility Impossible to randomize: In certain cases, you cannot perform an experiment because it is impossible to randomly assign people to particular groups. For example, the zoo keeper in Lesson 3 would not be able to assign a gender to each elephant.

  5. In the next activity, you will identify whether the research question could better be answered via an experiment or an observational study. Click on the document name to download a fillable copy of the What Should We Do? handout (LMR_3.3) and complete it.

  6. Now that you've completed the What Should We Do? handout, compare your answers with the sample below. If you were convinced by the sample and you had a different response for a scenario, go back to the handout and change your response.

  7. You will now generate three research questions like the ones in the scenarios. You need to identify the best data collection method for answering each question, and you should provide an explanation. At least one of the three research questions should use an observational study for data collection. Write your questions and explanations in your IDS Journal.

  8. Share your three research questions with a family member or friend. Ask them if they agree with your data collection method and explanation for each question. If not, discuss the reasons why they disagree with you.

Reflection

What are the essential learnings you are taking away from this lesson?