Scatter Plots
4-7 Scatter
Insert Lesson
Plots Title Here
Vocabulary
scatter plot
correlation
line of best fit
Course 3
4-7 Scatter Plots
A scatter plot shows relationships between
two sets of data.
Course 3
4-7 Scatter Plots
Additional Example 1: Making a Scatter Plot of a Data Set
Use the given data to make a scatter plot of the weight and height of each
member of a basketball team.
The points on the scatter plot are (71, 170), (68,
160), (70, 175), (73, 180), and (74, 190).
Course 3
4-7 Scatter Plots
Correlation describes the type of relationship between two data sets. The
line of best fit is the line that comes closest to all the points on a scatter plot.
One way to estimate the line of best fit is to lay a ruler’s edge over the graph
and adjust it until it looks closest to all the points.
Course 3
4-7 Scatter Plots
Positive correlation;
both data sets increase
together.
Course 3
No correlation; as one
data set increases, the
other decreases.
Negative correlation; as
one data set increases,
the other decreases.
4-7 Scatter Plots
Additional Example 2A: Identifying the Correlation of Data
Do the data sets have a positive, a negative, or no correlation?.
A. The size of a jar of baby food and the
baby will eat.
number of jars of baby food a
Negative correlation: The more food in each jar, the fewer number of jars of
baby food a baby will eat.
Course 3
4-7 Scatter Plots
Additional Example 2B: Identifying the Correlation of Data
Do the data sets have a positive, a negative, or no correlation?.
B. The speed of a runner and the number of
races she wins.
Positive correlation: The faster the runner, the more races she will win.
Course 3
4-7 Scatter Plots
Additional Example 2C: Identifying the Correlation of Data
Do the data sets have a positive, a negative, or no correlation?.
C. The size of a person and the number of fingers he has
No correlation: A person generally has ten fingers regardless of their size.
Course 3
4-7 Scatter Plots
Try This: Example 2A
Do the data sets have a positive, a negative, or no correlation?.
A. The size of a car or truck and the number of miles per gallon of
gasoline it can travel.
Negative correlation: The larger the car or truck, the fewer miles per gallon
of gasoline it can travel.
Course 3
4-7 Scatter Plots
Try This: Example 2C
Do the data sets have a positive, a negative, or no correlation?.
C. The number of telephones using the same phone number and the
number of calls you receive.
No correlation: No matter how many telephones you have using the same
telephone number, the number of telephone calls received will be the
same.
Course 3
4-7 Scatter Plots
Additional Example 3: Using a Scatter plot to Make Predictions
Use the data to predict how much a worker will earn in tips in 10 hours.
According to the graph, a worker will earn
approximately $24 in tips in 10 hours.
Course 3
4-7 Scatter Plots
Try This: Example 3
Use the data to predict how many circuit boards a worker will assemble in
10 hours.
14
12
10
8
6
4
2
2 4 6 8 10 12 14
Circuit Board
Assemblies
Course 3
According to the graph, a worker will
assemble approximately 10 circuit boards
in 10 hours.
Scatter Plot
• A scatter plot is a graph of a collection of
ordered pairs (x,y).
• The graph looks like a bunch of dots, but some
of the graphs are a general shape or move in a
general direction.
Positive Correlation
• If the x-coordinates and the
y-coordinates both
increase, then it is
POSITIVE CORRELATION.
• This means that both are
going up, and they are
related.
Positive Correlation
• If you look at the age of a child and the
child’s height, you will find that as the
child gets older, the child gets taller.
Because both are going up, it is
positive correlation.
Negative Correlation
• If the x-coordinates and the ycoordinates have one
increasing and one
decreasing, then it is
NEGATIVE CORRELATION.
• This means that 1 is going up
and 1 is going down, making
a downhill graph. This means
the two are related as
opposites.
Negative Correlation
• If you look at the age of your family’s car and
its value, you will find as the car gets older, the
car is worth less. This is negative correlation.
No Correlation
• If there seems to be
no pattern, and the
points looked
scattered, then it is no
correlation.
• This means the two
are not related.
No Correlation
• If you look at the size shoe
a baseball player wears,
and their batting average,
you will find that the shoe
size does not make the
player better or worse,
then are not related.
Scatterplots
Which scatterplots below show a linear trend?
a)
c)
Negative
Correlation
e)
Positive
Correlation
b)
d)
f)
Constant
Correlation
Objective - To plot data points in the
coordinate plane and interpret scatter
plots.
y
Sport Utility Vehicles
(SUVs) Sales in U.S.
5
Year Sales (in Millions)
4
1991
1992
1993
1994
1995
1996
1997
1998
1999
0.9
1.1
1.4
1.6
1.7
2.1
2.4
2.7
3.2
3
2
1
1991 1993 1995 1997 1999
1992 1994 1996 1998 2000
Year
x
Scatterplot - a coordinate graph of data points.
Trend appears linear.
y
5
Trend is increasing.
4
Year 
SUV Sales 
3
Positive correlation.
1
Predict the sales in 2001.
2
1991 1993 1995 1997 1999
1992 1994 1996 1998 2000
Year
x
Describe the relationship between time spent on
homework and time spent watching TV.
Trend appears linear.
Trend is decreasing.
240
210
180
150
120
90
Time on TV 
60
Time on HW 
30
Negative correlation.
30
90
150
210
60
120
180
240
Time Watching TV
Line of Best Fit
• A line of best fit is a line that best
represents the data on a scatter plot.
• A line of best fit may also be called a trend
line since it shows us the trend of the data
– The line may pass through some of the
points, none of the points, or all of the points.
– The purpose of the line of best fit is to show
the overall trend or pattern in the data and to
allow the reader to make predictions about
future trends in the data.
1. Prepare a scatter plot of the data on graph paper.
Use the data to create a scatter plot
Fat Grams and Calories in Food
700
600
Total Calories
2. Using a
straight edge,
position it so that
the plotted points
are as close to the
line as possible.
DRAW A LINE.
500
400
300
200
100
0
0
5
10
15
20
25
Total Fat Grams
3. Find two points that you think will be on the "best-fit" line.
Perhaps you chose the points (9, 260) and (30, 530).
Different people may choose different points. All of them are "correct“.
30
35
40
Fat Grams and Calories in Food
700
4. Write the
equation of
the line.
Total Calories
600
500
400
300
200
100
0
0
5
10
15
20
25
30
35
40
Total Fat Grams
5. This equation can now be used to predict information that was not plotted in the
scatter plot. For example, you can use the equation to find the total calories based
upon 22 grams of fat.
If you have 22 grams of fat in your food, the it will also be about 427.141 calories.