1. Scatter Plots - Line of Best Fit
Presented by Mr. Laws
JCMS

2. Standard
8.SP.2 – Linear regression & lines of best fit: Know that straight lines are widely used to model relationships between two quantitative variables. For scatter plots that suggest a linear association, informally fit a straight line, and informally assess the model fit by judging the closeness of the data points to the line.

3. Essential question
How do I draw a line of best fit to help show a linear association and a general trend between a set of scatter plot data?

4. Key Vocabulary words
Line of Best Fit – it is a line drawn to help show a linear association between a set of data. It is also known as a trend line.
Linear Regression – is a line drawn through a set of data that helps make a prediction between value of dependent variable (y) and the value of the independent variable (x).
Equation of the Line – Slope Intercept Form (y = mx + b).

5. What is a line of best fit?
It is straight line that is drawn informally between a set of scatter plot data to help assess the closeness of the data points to the line.
It helps make a prediction based on the linear association between two quantitative variables (x and y).
Its known as a trend line, line of regression, equation of a line (y = mx + b), or slope.

6. How do I draw a line of best fity
Step 1: Draw a straight line between the scatter plots cluster. Make sure there are as many plots above or below the line.
*Also make sure the line models the flow of the cluster of plots – going upward if positive, going downward if negative.
Line of Best Fit x x x

7. How do I draw a line of best fit
Are these line of best fit drawn correctly? If not, explain why? x y x y

8. How do I draw a line of best fit to help make a prediction?
Math Test Scores vs Hours Studied
Hours Studied (x) .5 1 2
1.5 3 4 5 6
Test Scores (y) 50 55 60 70 65 80 85 90
100
What is the relationship between hours studied and predicted test scores? Positive, negative, or no relationship?

9. How do I draw a line of best fit to help make a prediction?
Math Test Scores vs Hours Studied
Hours
Scores 1 2 3 4 6 5 50 60 70 80 90
100
Step 1 : Plot all the data
Step 2: Draw a line of best fit
The line of best fit will help you make a prediction on scores verses hours of the data set.

10. How do I draw a line of best fit to help make a prediction?
Math Test Scores vs Hours Studied
Hours
Scores 1 2 3 4 6 5 50 60 70 80 90
100
What is the predicted score if a students study for 2.5 hours?
Approx. 72% or 73%

11. How do I draw a line of best fit to help make a prediction?
Math Test Scores vs Hours Studied
Hours
Scores 1 2 3 4 6 5 50 60 70 80 90
100
If a student received a 88%, how many hours did he or she studied?
Approx. 4.3 hours

12. Summary What have you learn in this lesson?
What are the keys things to remember about this lesson?
Is there any thing else you would like to know about this lesson?