Learn to display and analyze data in scatter plots'

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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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Try This Example 1
Use the data to make a scatter plot. Describe the
relationship between the data sets.
10,000 8,000 6,000 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 cost on the vertical axis.
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Try This Example 1 Continued
Step 2 Plot a point from each pair of values.
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Try This 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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Try This 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 Variables
Write positive correlation, negative correlation,
or no correlation to describe each relationship.
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 Variables
Write positive correlation, negative correlation,
or no correlation to describe each relationship.
The graph shows that as the year increases, sales
decrease. So the graph shows a negative
correlation between the data sets.
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Additional Example 2C Determining Relationships
Between Two Variables
Write positive correlation, negative correlation,
or no correlation to describe each relationship.
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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Try This 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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Try This 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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Try This 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 1
1. The table shows the daily attendance at the
beach. Use the data to make a scatter plot of the
data and describe the relationship between the
data sets.
The graph shows a positive correlation.
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Lesson Quiz Part 2
2. Write positive, negative, or no correlation to
describe the relationship shown.
negative correlation