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## Chapter 3 - Day 3

• ##### Estimate the correlation between two quantitative variables from a scatterplot.
• Interpret the correlation.

• Distinguish correlation from causation.

##### Activity:

Experience First

In the previous lesson, students learned to describe the relationship between two quantitative variables by addressing direction, form, strength, and outliers. Today, we will focus in on the idea of strength by introducing the correlation r, which is a numerical value of the strength of a linear relationship.

Before starting the activity, have students look at these examples so they can start to get a feel for correlation. Ask them “What do you notice?”

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Students should stop after question 3 in the activity, at which point the teacher will do the debrief.

The teacher will then lead question #4. For this competition, use the random scatterplot generator on the Generate a random scatterplot for the first group, have them collaborate within the group and then make a guess. Record how far their guess was from the actual r. Do this same thing for each group in the room. The group who is closest to the actual r wins the prize (candy always works).

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Formalize Later

The third learning target to distinguish correlation from causation is NOT contained within the activity, but instead shows up in the Check Your Understanding problem. This might be the most important takeaway of the entire school year! See this blog post for more ideas on how to teach this, and make sure you go through some of the examples on Tyler Vigen’s website Spurious Correlations.

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