Chi-Square Test for Independence (Topics 8.5-8.6)
Chapter 11 - Day 5 - Lesson 11.2
Learning Targets
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Perform a chi-square test for independence.
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Choose the appropriate chi-square test in a given setting.
Activity: Are Taco Tongue and Evil Eyebrow Independent?
Activity:
Answer Key:
Stats Medic / Skew the Script Collaboration Lesson: Was “Stop and Frisk” Biased?
Activity:
Answer Key:
There is really nothing new that students need to complete this activity. All of the mechanics of the chi-square test for independence are the same as the chi-square test of homogeneity from yesterday.
How Do I Know Which Chi-square Test?
To help organize their thinking about the three different chi-square tests, students should consider the number of variables and number of populations.
Chi-square test for goodness of fit: 1 variable, 1 population.
Chi-square test for homogeneity: 1 variable, 2+ populations/treatments.
Chi-square test for independence: 2 variables, 1 population.
Context Matters!
To help students remember the difference between the three chi-square tests, urge them to recall the context that we used in class to introduce the test. Here are the contexts that we used in the text:
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M&M’S –> Chi-square test for goodness of fit
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Gummy bears –> Chi-square test for homogeneity
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Evil Eyebrow and Taco Tongue –> Chi-square test for independence
Final Note
The 2016 and 2017 AP Statistics Exams each had a free response question that asked students to do a chi-square test. So this means that it will not be on the 2018 AP Exam (wait…unless each exam is independent of the previous ones).
Luke's Lesson Notes
Here is a brief video highlighting some key information to help you prepare to teach this lesson.