Lesson objective: Determine a line of best fit for a scatter plot by using two points to find the equation of a line.
This lesson helps to build procedural skill with a line of best fit. A scatter plot is used here because it highlights the linear association between the variables. This work develops students' understanding that bivariate data may not have an exact linear association, but a linear model if often used to describe the association.
Students engage in Mathematical Practice 5 (Use appropriate tools strategically) as they use a scatter plot to decide which points best represent the linear association between variables and use those points to find an equation of the line of best fit.
Key vocabulary:
 bivariate data
 dependent variable
 horizontal change
 independent variable
 intercept
 line of best fit
 linear association
 linear model
 negative association
 patterns of association
 positive association
 slope
 vertical change

yintercept
Special materials needed:
 uncooked spaghetti noodle or another thin straight edge