Exercise 4 Page 195

Remember, this is only one example of a real life data set. Data is available in many forms all over the place! Statistics is real!

According to the United States Forest Service (USFS), the cost of emergency fire suppression over time is modeled by the following scatter plot.

The data points show the amount of money spent on fire suppression, in dollars, between $1980$ and $1999.$ The trend of the data seems to be a weak, positive correlation. To draw a line of fit, we should mark a line where we think it goes through the middle of most of the points.

To write an equation for this line of fit in slope-intercept form $y=mx+b,$ we need to find the slope and the $y\text{-}$intercept. Because we would need to approximate the $y\text{-}$intercept, let's begin with the slope. The line perfectly passes through the intersection of graph lines at the points $(5,500)$ and $(15,750).$ We can use these to solve for the slope. Now we can use the slope and one of the points, $(5,500),$ to solve for $b.$ Finally, we can write the final equation of our line: