Scatter Plots
A scatter plot is a graph with points plotted to show
a relationship between two sets of data.
Making a scatter plot of a data set:
A teacher surveyed her students about the amount
of physical activity they get each week. She then
had their body mass index (BMI) measured. Use her
data to make a scatter plot.
B M I
Active Hrs
Student per week BMI
A
10
16
B
3
25
C
6
24
D
8
10
E
10
16
F
8
18
G
7
21
H
2
28
I
19
9
J
14
12
3 5
3 0
2 5
2 0
1 5
1 0
5
0
4
8
12
Hours
16
20
24
Height
71
68
70
73
74
Weight
170
160
175
180
190
weight
Use the given data
to make a scatter
plot of the weight
and height of each
member of a
basketbal team.
(lb)
Correlation describes the relation between two sets
of data.
190
180
170
160
0
68
70
72
height
74
76
(in)
78
80
strong
weak
Positive Correlation:
both data sets
increase together.
weak
strong
Negative Correlation: as
No Correlation:
one data set increases,
changes in one
the other decreases
data set do not
affect the
other data set.
Do the data sets have a positive, a negative, or no correlation?
Examples:
1. The age and weight of a baby
As a baby gets older his weight ________. Both sets of data
________, so the data has a __________ correlation.
2. The amount of free time you have and the number of sports
that you play
Your free time _________ as the number of sports you play
________; therefore, the data has a ________ correlation.
3. The price of a shirt and the color of its buttons
The price is not affected by the color of its buttons so the
data has _________ correlation.
Do the data sets have a positive, a negative, or no correlation?
A: The number of hours a plane is in flight and the number of
miles flown
Positive correlation: The longer a plane is in flight, the
more miles it flies.
B: The number of hours in flight and the number of passengers
No correlation: The number of hours in flight does not
affect the number of passengers on the plane.
C: The number of hours in flight and the gallons of fuel remaining
Negative correlation: The longer a plane is in flight, the
less fuel it has.
D: The size of a jar of baby food and the number of jars a
baby will eat
negative correlation
E: The speed of a runner and the number of races she wins
positive correlation
F: The size of a person and the number of fingers he has
no correlation
a)
b)
c)
d)
a horizontal line
a positive slope line
a negative slope line
no line of best fit
# of years you expect to live
Janie wants to make a scatter
plot comparing the life
expectancy (vertical axis) and
the number of cigarettes
smoked (horizontal axis). What
type of line of best fit should
Janie expect her scatter plot
to show?
# of cigarettes smoked
Use the data to
predict the
exam grade for
a student who
studies 10 hours
per week.
5
80
Grade
Hours Studied
Exam Grade
9
95
3
75
12
98
1
70
9 0
7 0
5 0
0
2
4
6
8
10
12
Hours
According to the graph, a student who studies 10 hours per
week should earn a score of about 95.
Hours
4
Tips ($) 12
8
20
3
7
2
7
11
26
2
2
2
2
$ earned
How much
will a worker
earn in tips
in 10 hours
according to
the data?
8
6
4
2
2 0
1 8
1 6
1 4
1 2
1 0
8
6
4
2
0
1
2
3
4
5
6
7
8
9
# of hours worked
approximately
$24
10
11 12