scatter plots
TRANSCRIPT
7-9 Scatter Plots
Course 2
Warm UpWarm Up
Problem of the DayProblem of the Day
Lesson PresentationLesson Presentation
Warm UpWhich of the following pairs do you think have a cause-and-effect relationship?
1. height and age2. hand span and address3. grade average and shoe size4. temperature and date
Course 2
7-9 Scatter Plots
yesno
noyes
Problem of the Day
From the pizza shop, James walks 12 blocks south, 22 blocks east, 18 blocks north, and 30 blocks west. What is the least number of blocks that he must travel if he returns to the pizza shop?
Course 2
7-9 Scatter Plots
14
Learn to display and analyze data in scatter plots.
Course 2
7-9 Scatter Plots
Vocabularyscatter plotpositive correlationnegative correlationno correlation
Course 2
7-9 Scatter Plots
To find out if two sets of data may be related, you can make a scatter plot of the data values in each set.
A scatter plot has two number lines, called axes—one for each set of data values.
Each point on the scatter plot represents a pair of data values. These points may appear to be scattered or may cluster in the shape of a line or a curve.
Course 2
7-9 Scatter Plots
Use the data to make a scatter plot. Describe the relationship between the data sets.
Additional Example 1: Making a Scatter Plot
Course 2
7-9 Scatter Plots
Type U.S. Only Rest of World
Mammals 63 251
Birds 78 175
Reptiles 14 64
Amphibians 10 8
Fishes 70 11
Clams 61 2
Number of Endangered Species
Step 1: Determine the scale and interval for each axis. Place the number of animals endangered in the U.S. on the horizontal axis and the number of animals endangered in the rest of the world on the vertical axis.
0 20 40 60 80
300 240
180
120 60 0
Additional Example 1 Continued
Course 2
7-9 Scatter Plots
Type U.S. Only Rest of World
Mammals 63 251
Birds 78 175
Reptiles 14 64
Amphibians 10 8
Fishes 70 11
Clams 61 2
Number of Endangered Species
Step 2: Plot a point for each pair of values.
0 20 40 60 80
300 240
180
120 60 0
Use the data to make a scatter plot. Describe the relationship between the data sets.
Additional Example 1 Continued
Course 2
7-9 Scatter Plots
Type U.S. Only Rest of World
Mammals 63 251
Birds 78 175
Reptiles 14 64
Amphibians 10 8
Fishes 70 11
Clams 61 2
Number of Endangered Species
Step 3: Label the axes and give the graph a title.
0 20 40 60 80
300 240
180
120 60 0
U.S.
Rest
of
Worl
d
Number of Endangered Species
Use the data to make a scatter plot. Describe the relationship between the data sets.
Additional Example 1 Continued
Course 2
7-9 Scatter Plots
Type U.S. Only Rest of World
Mammals 63 251
Birds 78 175
Reptiles 14 64
Amphibians 10 8
Fishes 70 11
Clams 61 2
Number of Endangered Species
There appears to be no relationship between the data sets.
0 20 40 60 80
300 240
180
120 60 0
U.S.
Rest
of
Worl
d
Number of Endangered Species
Check It Out: Example 1
Course 2
7-9 Scatter Plots
Step 1: Determine the scale and interval for each axis. Place the year on the horizontal axis and the number of farm workers on the vertical axis.
1940 1960 1980 2000
10,000
8,000
6,000
4,000
2,000
1940 8,9951950 6,8581960 4,1321970 2,8811980 2,8181990 2,864
Number of farm workers in thousands
Year
Use the data to make a scatter plot. Describe the relationship between the data sets.
Check It Out: Example 1 Continued
Course 2
7-9 Scatter Plots
Step 2: Plot a point from each pair of values.
1940 8,9951950 6,8581960 4,1321970 2,8811980 2,8181990 2,864
Number of farm workers in thousands
Year
1940 1960 1980 2000
10,000
8,000
6,000
4,000
2,000
Check It Out: Example 1 Continued
Course 2
7-9 Scatter Plots
Step 3: Label the axes and give the graph a title.Year
Num
ber
(in t
housa
nds)
Number of Farm Workers
1940 8,9951950 6,8581960 4,1321970 2,8811980 2,8181990 2,864
Number of farm workers in thousands
Year
1940 1960 1980 2000
10,000
8,000
6,000
4,000
2,000
Check It Out: Example 1 Continued
Course 2
7-9 Scatter Plots
The number of farm workers decreased from 1940 to 1970.
1940 8,9951950 6,8581960 4,1321970 2,8811980 2,8181990 2,864
Number of farm workers in thousands
Year
Year
Num
ber
(in t
housa
nds)
Number of Farm Workers
1940 1960 1980 2000
10,000
8,000
6,000
4,000
2,000
There are three ways to describe data displayed in a scatter plot.
Course 2
7-9 Scatter Plots
Positive Correlation
The values in both data sets increase at the same time.
Negative Correlation
The values in one data set increase as the values in the other set decrease.
No Correlation
The values in both data sets show no pattern.
Write positive correlation, negative correlation, or no correlation to describe each relationship. Explain.
Additional Example 2A: Determining Relationships Between Two Sets of Data
Course 2
7-9 Scatter Plots
The graph shows that as area increases, population increases. So the graph shows a positive correlation between the data sets.
Write positive correlation, negative correlation, or no correlation to describe each relationship. Explain.
Additional Example 2B: Determining Relationships Between Two Sets of Data
Course 2
7-9 Scatter Plots
The number of vacation days is not related to height. So there would not be any correlation between these two variables.
height and number of vacation days
Write positive correlation, negative correlation, or no correlation to describe each relationship. Explain.
outdoor temperature and coat sales
Additional Example 2C: Determining Relationships Between Two Sets of Data
Course 2
7-9 Scatter Plots
As the outdoor temperature increases, the number of coat sales will decrease. So there would be a negative correlation between the data sets.
Write positive correlation, negative correlation, or no correlation to describe each relationship.
Check It Out: Example 2A
Course 2
7-9 Scatter Plots
Tornado Frequency
0
200
400
600
800
1000
1200
1940 1960 1980 2000
Year
Nu
mb
er
of
To
rna
do
s
The graph shows that as the year increases, number of tornados increases. So the graph shows a positive correlation between the data sets.
Write positive correlation, negative correlation, or no correlation to describe each relationship.
Check It Out: Example 2B
Course 2
7-9 Scatter Plots
Guitar String Frequency
200
300
400
500
600
700
40 60 80 100 120
Length of string (cm)
Fre
qu
en
cy
(vp
s)
The graph shows that as the length of string increases, frequency decreases. So the graph shows a negative correlation between the data sets.
vps = vibrations per second
Write positive correlation, negative correlation, or no correlation to describe each relationship.
Check It Out: Example 2C
Course 2
7-9 Scatter Plots
There would not be any correlation between these two variables.
eye color and age
Lesson Quiz: Part I
1. Use the data to make a scatter plot. Describe the relationship.
Course 2
7-9 Scatter Plots
Temperature Attendance
70 100
80 350
75 250
85 400
74 200
82 375
72 260
Beach Attendance
0
100
200
300
400
500
70 75 80 85
Temperature
Att
en
da
nc
e
The graph shows a positive correlation.
Lesson Quiz: Part II
2. Write positive, negative, or no correlation to describe each relationship. Explain
Course 2
7-9 Scatter Plots
negative correlation; as age increases, attendance decreases.