1. Line of Best Fit
The line of best fit is the line that lies as close as possible to all the data points. Linear regression is a method for finding the equation of the regression line,
Remember:

2. Line of Best Fit On Graphing Calculator
First press STAT and 1:EDIT.
Enter the x- and y- coordinates in your calculator under L1 and L2.
Then hit STAT, CALC, and arrow down to
4: LinReg (ax+b) and Press ENTER
Should say xlist: L1
ylist: L2 Hit ENTER 5 times
Arrow down and “a” is the slope of the line of best fit, “b” is the y-intercept

3. Ex. 1. The table shows the cost of a catered lunch buffet for different numbers of people. Find the LOBF for the data.
# of people 12 18 24 30 36 42
Costs
192
288
384
480
576
672
a = 16
b = 0
y = 16x

4. 2.
Ex: The table gives the average class score y on each unit test for the first 6 units of CRM. Approximate the best fitting line for the data. x 1 2 3 4 5 6 y 84 83 86 88 87 90
a = 1.3
b = 81.9
y = 1.3x
If the trend continues, what would be the average score on the 8th unit exam? (This is called extrapolation)

5. 3.
Ex: The ordered pairs (x, y) give the height y in feet of a young tree x years after Approximate the best fitting line for the data.
(0,5.1), (1,6.4), (2,7.7), (3,9), (4,10.3), (5,11.6), (6,12.9)
a = 1.3
b = 5.1
If the trend continues, what would be the height of the tree after 9 years?

6. 4.
Ex: The table below gives the number of people y who attended each of the first seven football games x of the season. Approximate the best-fitting line for the data. x 1 2 3 4 5 6 7 y
722
763
772
826
815
857
897
a = 27
b = 699.4
If the trend continues, what would be number of people attending the 10th game?

7. Remember y= mx + b This is slope-intercept form of a line.
Remember slope can be positive or negative.
Remember that b tells the y-intercept (where the line crosses the y-axis)

8. 5. Which of the following could be a line of best fit for the following scatter plot?
y = 1.5x + 19
y = 1.5x – 19
y =
y = -1.5 – 19

9. 6. Which of the following could be a line of best fit for the following scatter plot?
y = -16.7x
y = -16.7x +18.9
y =
y = 16.7 – 18.9

10. 7. Which of the following could be a line of best fit for the following scatter plot?
y = 6.7x – 57.9
y = 6.7x
y =
y = -6.7 – 57.9