Line of Best Fit

1
Line of Best Fit

• SOL A.16 - Given a set of data points, write an
  equation for a line of best fit and use the
  equation to make predictions. 

2
Scatter Plot

• A scatter plot shows a relationship between
  paired data
• There may be a positive or negative pattern OR no
  pattern at all

3
What type of relationship exists between x and y?

• No relationship
• Negative
• Positive
• None of the above

4
Line of Best Fit

• Consider the graph below.
• What would y be if x9?
• What would x be if y10?

5
Line of Best Fit

• A line of best fit is a straight line that best
  represents the data on the scatter plot
• Can be used to predict data values

6
Which graph shows the line of best fit for the
data?

• Graph 1
• Graph 2
• Graph 3

Graph 1
Graph 2
Graph 3
7
Example 1 The average California Achievement
Test scores in mathematics and science for Wesley
High School sophomores from 1985 to 1989 are
given in the table below.

• Make a scatter plot of the data.
• Is there a relationship? Positive or Negative?
• Predict the math score corresponding to a science
  score of 50.
• Predict the science score corresponding to a math
  score of 65.

8
Calculator Skill Scatter Plot

• Use the data from the table in Example 1.
• Step 1 Choose STAT
• from MAIN MENU
• Step 2 Enter each set of data
• into List 1 and List 2
• Step 3 Choose GRPH (F1),
• then F1 again (GPH1)

• Use the data from the table in Example 1.
• Step 1 Choose STAT
• from MAIN MENU
• Step 2 Enter each set of data
• into List 1 and List 2
• Step 3 Choose GRPH (F1),
• then F1 again (GPH1)

9
Calculator Skill Best Fit Line

• Step 4 Choose CALC (F1),
• then choose X (F2)
• Step 5 Choose DRAW (F6)
• Note The equation of the line
• is in slope-intercept form.
• Now you have graphed the data
• points and their line of best fit.

10
Calculator Skill Best Fit Line

• Make predictions using your equation!
• Step 6 Choose COPY (F5) and EXE. Note The
  equation of the line
• is pasted in the GRAPH menu.
• Step 7 Select TABLE from the main menu. You
  should see your equation pasted. Choose TABL
  (F6) to type in prediction values.

11
Homework

• Line of best fit