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partner’s arguments. The rst few times students engage in these activities, the teacher should demonstrate, with a partner, how the discussion is expected to go. Once students are familiar with these structures, less set-up will be necessary. While students are working, the teacher can ask students to restate their question more clearly or paraphrase what their partner said.
Why: Building in an expectation, through the routine, that students explain the rationale for their choices and listen to another's rationale deepens the understanding that can be achieved through these activities. Specifying that students take turns deciding, explaining, and listening limits the phenomenon where one student takes over and the other does not participate. Taking turns can also give students more opportunities to construct logical arguments and critique others’ reasoning (MP3).
Launch
Tell students that the value is called a correlation coe cient. It is one way to measure the strength of a linear relationship. Tell students that:
1. the sign of is the same as the sign of the slope of the best t line
2. the values for go from -1 to 1, inclusive
3. the closer is to 1 or -1, the stronger the linear relationship between the variables 4. the closer is to 0, the weaker the linear relationship between the variables
Arrange students in groups of 2. Tell students that for each scatter plot, one partner nds the associated correlation coe cient and explains why they think it goes with that scatter plot. The other partner's job is to listen and make sure they agree. If they don't agree, the partners discuss until they come to an agreement. For the next scatter plot, the students swap roles. If necessary, demonstrate this protocol before students start working.
Student Task Statement
1. Take turns with your partner to match a scatter plot with a correlation coe cient.
2. For each match you nd, explain to your partner how you know it’s a match.
3. For each match your partner nds, listen carefully to their explanation. If you disagree, discuss your thinking and work to reach an agreement.
Unit 3
Lesson 7: The Correlation Coe cient 113