Lesson 2: 4.2 Sampling: Good and Bad
Duration of Days: 2
Lesson Objective
Students will be able to identify variable sampling methods (Convenience and Voluntary Response) and explain how these methods lead to bias.
1. If I only interview people at the mall, why is my data "poisoned"?
2. Why do people with strong negative opinions love to respond to surveys?
Bias
Convenience Sampling
Voluntary Response Sampling
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 loves "Bias" questions. They will describe a flawed sampling method (like a radio call-in show) and ask if the results are valid for the general public.
This section is about "Data Disasters." It teaches students that the size of a sample doesn't matter if the method of choosing it is flawed.
The Problem: An online news site asks readers: "Do you support the new tax law?" 85% of the 10,000 respondents say "No."
Task: Explain why this 85% might not represent the true opinion of all citizens.
"More is Better": Students think 10,000 voluntary responses are better than 100 random ones.
Support: Use the "Soup Analogy." If you don't stir the pot (randomize), one spoonful (sample) won't tell you how the whole pot tastes.
Teacher assigns examples from the textbook and other resources.
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