1. Line of Best Fit

2. Sometimes points on a scatter plot are represented by a trend line or a
___________________.
You can study the line to see how the data behaves. You may have a basis predict what the data might be for values not given.
line of best fit

3. Line of Best Fit
Line of Best Fit is a line that approximates a trend for the data in a scatter plot. It shows pattern and direction

4. Line of Best Fit
a line that approximates a trend for the data in a scatter plot
shows pattern and direction

5. How to Find the Line of Best Fit
The line of best fit should:
pass through as many points as possible
allow remaining points to be grouped equally above and below the line

6. Draw the line of best fit for the following scatter plots:

7. Draw the line of best fit for the following scatter plots:

10. Why make a Line of Best Fit?
Helps us to make predictions by
INTERPOLATING
EXTRAPOLATING

11. Interpolating: Estimating a value BETWEEN two measurements in a set of data
Extrapolating: Estimating a value BEYOND the range of a set of data
Helps us determine if it is a weak or strong correlation.

12. Interpolating – what would the wife’s age be of a husband who is 57?
Extrapolating - what would the wife’s age be of a husband who is 84?

13. If the data points are close to the line of best fit, it is said to have a ___________correlation.
strong
strong positive
weak positive
strong negative
weak negative

14. Use the line of best fit to predict how many tornadoes may be reported in the United States in 2015 if the trend continues.
1200
1000
800
600
If the trend continues we predict that there will be 1200 tornadoes reported in 2015.
400
200
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
2015

15. Finding the Line of BEST Fit
Usually there is no single line that passes through all the data point, so you try to find the line that best fits the data.
Step 1: using a ruler, place it on the graph to find where the edge of the ruler touches the most points.
Step 2: Draw in the line. Make sure it touches at least 2 points.

16. Finding the Line of BEST Fit (continued)
Step 3: Find the slope between two points
Step 4: Substitute that into slope- intercept form of an equation and solve for “b.”
Step 5: Write the equation of the line in slope-intercept form.

17. Let’s try one: SANDWICH Total Fat (g) Total Calories Grilled Chicken 5
300
Hamburger 9
260
Cheeseburger 13
320
Quarter Pounder 21
420
Quarter Pounder with Cheese 30
530
Big Mac 31
560
Arch Sandwich Special
550
Arch Special with Bacon 34
590
Crispy Chicken 25
500
Fish Fillet 28
Grilled Chicken with Cheese 20
440