Scatter Plots

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Scatter Plots
Warm Up
Problem of the Day
Lesson Presentation
Course 2
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Warm Up Which of the following pairs do you think
have a cause-and-effect relationship? 1. height
and age 2. hand span and address 3. grade
average and shoe size 4. temperature and date
yes
no
no
yes
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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?
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Learn to display and analyze data in scatter
plots.
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Vocabulary
scatter plot positive correlation negative
correlation no correlation
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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
axesone 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.
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Additional Example 1 Making a Scatter Plot
Use the data to make a scatter plot. Describe the
relationship between the data sets.
300 240 180 120 60 0
0 20 40 60 80
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.
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Additional Example 1 Continued
Step 2 Plot a point for each pair of values.
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Additional Example 1 Continued
Use the data to make a scatter plot. Describe the
relationship between the data sets.
Number of Endangered Species
Rest of World
U.S.
Step 3 Label the axes and give the graph a title.
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Additional Example 1 Continued
Use the data to make a scatter plot. Describe the
relationship between the data sets.
Number of Endangered Species
Rest of World
U.S.
There appears to be no relationship between the
data sets.
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Check It Out Example 1
Use the data to make a scatter plot. Describe the
relationship between the data sets.
10,000 8,000 6,000
4,000 2,000
1940 1960 1980 2000
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.
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Check It Out Example 1 Continued
Step 2 Plot a point from each pair of values.
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Check It Out Example 1 Continued
Number of Farm Workers
Number (in thousands)
Year
Step 3 Label the axes and give the graph a title.
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Check It Out Example 1 Continued
Number of Farm Workers
Number (in thousands)
Year
The number of farm workers decreased from 1940 to
1970.
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There are three ways to describe data displayed
in a scatter plot.
Positive Correlation
Negative Correlation
No Correlation
The values in both data sets increase at the same
time.
The values in one data set increase as the values
in the other set decrease.
The values in both data sets show no pattern.
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Additional Example 2A Determining Relationships
Between Two Sets of Data
Write positive correlation, negative correlation,
or no correlation to describe each relationship.
Explain.
The graph shows that as area increases,
population increases. So the graph shows a
positive correlation between the data sets.
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Additional Example 2B Determining Relationships
Between Two Sets of Data
Write positive correlation, negative correlation,
or no correlation to describe each relationship.
Explain.
height and number of vacation days
The number of vacation days is not related to
height. So there would not be any correlation
between these two variables.
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Additional Example 2C Determining Relationships
Between Two Sets of Data
Write positive correlation, negative correlation,
or no correlation to describe each relationship.
Explain. outdoor temperature and coat sales
As the outdoor temperature increases, the number
of coat sales will decrease. So there would be a
negative correlation between the data sets.
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Check It Out Example 2A
Write positive correlation, negative correlation,
or no correlation to describe each relationship.
The graph shows that as the year increases,
number of tornados increases. So the graph shows
a positive correlation between the data sets.
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Check It Out Example 2B
Write positive correlation, negative correlation,
or no correlation to describe each relationship.
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
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Check It Out Example 2C
Write positive correlation, negative correlation,
or no correlation to describe each relationship.
eye color and age
There would not be any correlation between these
two variables.
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Lesson Quiz Part I
1. Use the data to make a scatter plot. Describe
the relationship.
Temperature Attendance 70 100
80 350 75 250 85
400 74 200 82 375
72 260
The graph shows a positive correlation.
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Lesson Quiz Part II
2. Write positive, negative, or no correlation to
describe each relationship. Explain
negative correlation as age increases,
attendance decreases.