1-7 Scatter Plots
How can scatter plots help spot
trends?
Vocabulary
• scatter plot – a graph that shows the
relationship between two sets of data
Constructing a Scatter Plot
• In a scatter plot, two sets of data are graphed
as ordered pairs on a coordinate system.
• Choose something to represent on the x-axis,
and something to represent on the y-axis.
Example – Test Scores
The table shows the average SAT math scores
from 1990 – 2000.
Year 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000
Score 510 500 501 503 504 506 508 511 512 511 514
Make a scatter plot of the data.
Number of Rebounds
18
16
14
12
10
Number of Rebounds
8
6
4
2
0
0
5
10
15
The Table shows the average cost of a
loaf of bread from 1920 - 2000
Year 1920 1930 1940 1950 1960 1970 1980 1990 2000
Cents 12 9
8 14 20 24 52 72 99
Please make a scatter plot of the data.
Interpreting a Scatter Plot
Some types of relationships:
• No
Relationship
– No –obvious
patternsyy
Negative
Relationship
–As
Asxxincreases,
increases,
Positive
Relationship
decreases.
increases
Figures are from http://www.mste.uiuc.edu/courses/ci330ms/youtsey/scatterinfo.html.
Please determine whether a scatter plot of the data
for the following might show a positive, negative, or
no relationship.
Negative relationship
Please determine whether a scatter plot of the data
for the following might show a positive, negative, or
no relationship.
No relationship
Please determine whether a scatter plot of the data
for the following might show a positive, negative, or
no relationship.
Positive relationship
A zoologist studied extinction times (in years) of
island birds. The zoologist wanted to see if
there was a relationship between the average
number of nests and the time needed to each
bird to become extinct on the islands. Use the
table of data on the next slide to make a
prediction.
Bird Name
Average Number
Bird Size of Nests
Extinction Time
Buzzard
Large
2.0
5.5
Quail
Large
1.0
1.5
Curlew
Large
2.8
3.1
Cuckoo
Large
1.4
2.5
Magpie
Large
4.5
10.0
Swallow
Small
3.8
2.6
Robin
Small
3.3
4.0
Stonechat
Small
3.6
2.4
Blackbird
Small
4.7
3.3
Tree-Sparrow
Small
2.2
1.9