Teaching Notes 4.14: Finding the Equation of the
Line of Best Fit
The line of best fit is a line that can be drawn through points on a scatter plot to show a trend
between two sets of data. Many students find this concept abstract. Drawing a line suggested by
the points enables students to determine the equation of the line; however, the fact that there is
no exact answer can cause confusion.SPECIAL MATERIALS:
Graph paper, rulers- Explain that in real life data may not always lie in a straight line. In such cases, students have
to draw a line of best fit on a scatter plot that approximates the data. Not all of the points will
be on the line. - Offer an example of movie ticket prices students may purchase at various theaters. The
number of tickets represents thex-coordinate and the total paid for the tickets represents
they-coordinate. An example of an ordered pair might be (2, $12.00), which means
that two tickets cost $12.00. Ask your students to create a scatter plot by graphing the
following ordered pairs: (2, $12.00), (1, $7.00), (1, $6.50), (2, $9.00), (4, $28.00), (1, $7.50),
(3, $16.50), (4, $30.00), and (5, $25.00). Instruct them to draw the line of best fit and find
the equation of the line. Depending on their abilities, you might find it helpful to review
4.13: ‘‘Writing a Linear Equation, Given Two Points.’’ Because the lines of best fit of students
may vary, the equations may also vary. One possible answer isy= 6 x+ 0 .6. - Review the information on the worksheet with your students. Emphasize that the first
number of an ordered pair represents thex-coordinate and the second represents the
y-coordinate. Remind students that they must select two points on their line to find the
slope. If necessary, review rounding to the nearest tenth.
EXTRA HELP:
A line of best fit is also called the ‘‘best-fitting line.’’ANSWER KEY:
Answers will vary. Possible answers follow.(1)y= 1. 6 x+ 0. 8 (2)y= 0. 7 x− 0. 1 (3)y= 3. 3 x− 1. 1 (4)y= 0. 5 x+ 0. 3
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(Challenge)There is no way to tell if her equation would be very different. It depends on how close
those points were to her line.
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