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Designing Experiments

Chapter 4 - Day 6 - Lesson 4.2

Learning Targets
  • Describe the placebo effect and the purpose of blinding in an experiment.

  • Describe how to randomly assign treatments in an experiment using slips of paper, technology, or a table of random digits.

  • Explain the purpose of comparison, random assignment, control, and replication in an experiment.

Activity: Would You Fall for That? 
Answer Key:

Start by showing this video.

This activity is getting students to start thinking about the Caffeine Experiment, which we use as a review day before the Chapter 4 Test.

There are a lot of ideas in the learning targets in this lesson.  You have to be very intentional in the Debrief and Big Ideas to be sure that you are addressing all of them.

The Language of Experiments

Suppose that we thought that the temperature of the Coca Cola might also effect the pulse rate.  So not only are we using Coke and Caffeine Free Coke, we are also testing it at 35 degrees, 50 degrees, and 70 degrees.


Factor: A variable that is manipulated and may cause a change in the response variable (presence of caffeine and temperature).


Levels: The different values of the factors.  The factor “presence of caffeine” has two levels (yes and no) and the factor “temperature” has three levels (35, 50, and 70 degrees).


Treatments: A specific condition applied to the individuals in an experiment.  In this experiment, there are 6 treatments: (Yes, 35), (No, 35),  (Yes, 50), (No, 50), (Yes, 70), (No, 70).

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