standard_description: Understand that the graph of an equation in two variables is the set of all its solutions plotted in the coordinate plane, often forming a curve (which could be a line).
problem_activity: Problem 1
The scatterplot below displays the elevation and mean number of clear days per year of  U.S. cities. Two lines are shown on the scatterplot. Which represents the least squares line? Explain your choice.
[IMG]
Problem 2
Below is a scatter plot of foal birth weight and mare’s weight.
[IMG]
The equation of the least squares line for the data is
$${y=-19.6+0.248x}$$
, where
$$x$$
= mare’s weight (in kg) and
$$y$$
= foal’s birth weight (in kg).  What foal birth weight would you predict for a mare that weighs 520 kg?
How would you interpret the value of the slope in the least squares line?


aligns: no