Lesson objective: Understand that a linear model can be used to predict values in real-world problems.

Students bring prior knowledge of finding a line of best fit from 8.SP.A.2. This prior knowledge is extended to use the equation of the line of best fit as students predict values based on the line of best fit. A conceptual challenge students may encounter is understanding that they can not go too far out of the range of the independent and dependent variables to make predictions.

The concept is developed through work with scatter plot, which helps to support the use of a line of best fit to make predictions.

This work helps students deepen their understanding of equivalence because to show that a line of best fit predicts an equivalent answer for a value of the independent variable, which might not have been given as part of the data.

Students engage in Mathematical Practice 5 (Use appropriate tools strategically) as they use a line of best fit to predict information in real-world problems.

**Key vocabulary:**

- dependent variable
- independent variable
- line of best fit
- negative association
- patterns of association
- positive association