Chapter 10 Introduction
Activity: Murder or Coincidence?
We’ve made it! Chapter 10, the last chapter! In chapter 10, we introduce a new type of significance test, Chi-Square. We will be using Chi-Square tests for Goodness of Fit (GOF) and Chi-Square tests for Association. Both tests are used with categorical data so we can make some connections back to earlier learning, like looking for association with segmented bar graphs and conditional probability. We’ll also perform inference for the slope of an LSRL which allows us to revisit t-tests. It’s really a great chapter to end the year with.
Today we began by talking about Kristen Gilbert, a nurse whose patients were dying at an alarming rate. Do you think she is a murderer or was it just a coincidence? Begin the class by giving the students the activity page and having them read through the story, which is a clip from a news article. The likelihood of the deaths occurring at the same time as Gilbert’s shifts purely by chance (P-value) has been left out of the activity. Students will calculate this at the end of the chapter using a Chi-Square test. After the students read the story, give them 5-10 minutes to discuss in the group if they think Gilbert is a murderer and what other information they would need to know in order to make an informed decision. Facilitate a class discussion about their responses when they are done.
Because there are three different scenarios for tests this chapter, students may have some difficulty differentiating between which one to use in different contexts. Spend some time with students clearly outlining which test is used in different situations.
If your students have taken AP biology they may already be familiar with Chi-Square. Talk with the AP bio teacher to see what they covered.