In this activity, students individually sort cards of different scatter plots then discuss with a partner. Students sort different scatter plots during this activity. A sorting task gives students opportunities to analyze representations, statements, and structures closely and make connections (MP2, MP7).

Select groups to share their initial categories and how they sorted their scatter plots into the given categories. Attend to the language that students use to describe their categories and scatter plots, giving them opportunities to describe their scatter plots more precisely. Highlight the use of terms like “linear,” “non-linear,” and “positive or negative association.” 
To help clarify the meaning of non-linear association, consider asking:

• “How did you determine if an association is non-linear?” (if the data looks like it’s curving or not in a line)
• “Can a non-linear association show a positive association? What might that look like in a scatter plot?” (Yes, the scatter plot on card F is an example.)
• “If a scatter plot has no association at all (neither linear nor non-linear), what might its scatter plot look like?” (a lot of random dots scattered all around the plot with no obvious trend)

The goal of this discussion is to ensure students can make sense of the data given all the tools from this unit.

Consider asking some of the following questions:

• “Which data did you consider outliers?” (human and chimpanzee)
• “How did you determine your fitted line?” (I tried to get some points on either side of the line so that it would go through the middle of the points.)
• “Let’s assume the trend you found continues past the end of the scatter plot. A Tyrannosaurus rex is a dinosaur that is estimated to have a body weight of about 8,000 kg. What do you expect its brain weight to be?” (About 8,000 g, or 8 kg)

Based on the fossils of Tyrannosaurus rex and what they understand about the dinosaur’s anatomy, scientists believe that their brains would’ve weighed about 1 kilogram. The trend does not appear to continue, at least not in a linear way.