So you want to buy a
Author Rhonda Brooks
Identified Grade/Course Grade 8 – 12
Mathematical Concepts Scatter plots
PASS Objectives 2.1c, 2.2c.I, 2.2d, 3.1a, 3.1b, 3.2*
Lesson Summary This lesson would best be used after students have mastered writing
equations of lines from graphs. Students will be given classified ads
for Ford Mustangs and be asked to create a table and scatter plot,
describe the correlation, and use the line of best fit to make
predictions. They will also be asked to write the equation for the
line of best fit.
Placement within Unit Conclusion or assessment
Materials Needed Paper and pencil
Problem Situation Jacob is using the newspaper to shop for his first car. He wants to
(for students) buy a Ford Mustang. Below are the classified ads from the
Questions for Students 1. Make a table to represent this data.
2. Make a scatter plot for the given data using dollars (in
thousands) and number of
years (since 1998) for your axes.
Years (since 1998)
3. Yes. This data shows a positive correlation. As the year model
for the car goes up, the price goes up.
4. A 2003 would cost about $13,000, and a 2006 would cost about
$18,000. I determined where the given year model would cross the
line of best fit.
5. He could buy a 2002 Mustang or older.
6. The rate of change is $1,700 every year. The price of Ford
Mustangs increases about $1,700 each year.
7. The line of best fit would be approximately y=1700x + 4000.
The line of best fit represents the cost of an average car for any
given year model.
*** the rate of change and y-intercept will vary slightly depending
on accuracy of scatter plot and line of best fit
Scaffolding How will you organize the data in the table?
(Supporting) Questions What will you need to decide before you construct the scatter plot?
Extension Questions What are the factors that might cause new data to deviate
significantly from the line of best fit?
Can you think of a way that you could use scatter plots in your life?
If Jacob has a summer job that pays $7.00 per hour how many hours
would he need to work to be able to afford the 40th Anniversary
The formula to figure interest if I=PRT. Using this formula how
much interest would Jacob have to pay if he needed to borrow
$11,000 and had to pay an interest rate of 8%?
Other Information None Provided