Lesson 6: 4.6 How to Experiment Well
Duration of Days: 2
Lesson Objective
Students will be able to describe the four principles of experimental design: Comparison, Random Assignment, Control, and Replication.
Why is a "control group" necessary? (Compared to what?)
If we don't use random assignment, how do we know the groups were fair to begin with?
Control group
Random assignment
Replication
Placebo effect
Double-blind / Single-blind
HSS-IC.B.3: Recognize the purposes of and differences among sample surveys, experiments, and observational studies; explain how randomization relates to each.
The SAT expects students to recognize "The Placebo Effect." They might ask why a sugar pill is given to one group in a medical study.
Students learn the ingredients for a valid experiment. Without these four principles, the experiment's results are essentially meaningless.
The Problem: A scientist wants to test a new "brain booster" drink. He gives it to 20 students in an Honors class and gives water to 20 students in a Remedial class.
Task: Identify which principle of experimental design was violated and how to fix it.
Replication: Students think this means "doing the experiment again tomorrow." Clarify that it means using enough experimental units in each group to distinguish a pattern from a fluke.
Use the acronym CRRC (Comparison, Randomization, Replication, Control) as a checklist for every design prompt.
Teacher assigns examples from the textbook and other resources.
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