Lesson 11.4: Scatter Plots

1
Lesson 11.4 Scatter Plots

• Standards M7D1f M7A3a c
• Objective To construct a scatter plot and
  determine the relationship between two variables.
  

2
Scatter Plot

• A scatter plot is a graph of plotted points that
  shows if there is a relationship between two sets
  of data or two variables.
• The graph looks like a bunch of dots, but some of
  the graphs have a general shape or move in a
  general direction.

3
THE COORDINATE PLANE
y










This vertical line is called the y-axis.
4
THE COORDINATE PLANE
y
5
4
3
2
1
0
-1
-2
-3
-4
-5










This horizontal line is called the x-axis.
x
-5 -4 -3 -2 -1 0 1 2 3 4 5
5
THE COORDINATE PLANE
y
5
4
3
2
1
0
-1
-2
-3
-4
-5










The x-axis and y-axis separate the coordinate
plane into 4 parts.
x
-5 -4 -3 -2 -1 0 1 2 3 4 5
This point in the middle of the x-axis and y-axis
is called the origin.
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THE COORDINATE PLANE
y
5
4
3
2
1
0
-1
-2
-3
-4
-5










Quadrant II
Quadrant I
These parts are called Quadrants.
x
-5 -4 -3 -2 -1 0 1 2 3 4 5
Quadrant III
Quadrant IV
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THE COORDINATE PLANE
y
5
4
3
2
1
0
-1
-2
-3
-4
-5










To locate a point anywhere on the grid, you need
an ordered pair.
An ordered pair is a pair of numbers used to
locate points on a grid.
x
-5 -4 -3 -2 -1 0 1 2 3 4 5
( 1 , 3 )
The FIRST number is called the X- coordinate.
The SECOND number is called the Y- coordinate.
8
Construct a scatter plot to show the relationship
between the hours spent practicing shooting darts
and the dart shooting score.
Practice Time (hours) Dart Shooting Score Ordered pair to graph (x, y)
1 6 (1, 6)
2 8 (2, 8)
3 13 (3, 13)
4 20 (4, 20)
5 18 (5, 18)
6 27 (6, 27)
9
Construct a scatter plot to show the relationship
between the hours spent practicing shooting darts
and the dart shooting score.
Practice Time versus Dart Shooting Time
30
Ordered pair to graph (x, y)
(1, 6)
(2, 8)
(3, 13)
(4, 20)
(5, 18)
(6, 27)
25
20
Dart Shooting Score
15
10
5
0
0
1
2
3
4
5
6
Practice Time (hrs)
10
Positive Correlation

• If the x-coordinates and the y-coordinates both
  increase, then the two variables are said to have
  a POSITIVE CORRELATION.
• This means that both are going up, and they are
  related.

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Positive Correlation

• If you look at the age of a child and the childs
  height, you will find that as the child gets
  older, the child gets taller. Because both are
  going up, it is positive correlation.
• Can you think of any other examples of
• variables with a positive relationship?

Age 1 2 3 4 5 6 7 8
Height 25 31 34 36 40 41 47 55
12
Negative Correlation

• If the x-coordinates and the y-coordinates have
  one increasing and one decreasing, then the two
  variables are said to have a NEGATIVE
  CORRELATION.
• This means that 1 is going up and 1 is going
  down, making a downhill graph. This means the two
  are related as opposites.

13
Negative Correlation

• If you look at the age of your familys car and
  its value, you will find as the car gets older,
  the car is worth less. This is negative
  correlation.
• Can you think of anything else with
• a negative relationship?

Age of car 1 2 3 4 5
Value 30,000 27,000 23,500 18,700 15,350
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No Correlation

• If there seems to be no pattern, and the points
  looked scattered, then it is no correlation.
• This means the two are not related.

15
No Correlation

• If you look at the size shoe a baseball player
  wears, and their batting average, you will find
  that the shoe size does not make the player
  better or worse, then are not related.

16
Scatterplots
Which scatterplots below show a linear trend?
a)
c)
e)
Negative Correlation
Positive Correlation
b)
d)
f)
Constant Correlation
17
Objective - To plot data points in the coordinate
plane and interpret scatter plots.
y
Sport Utility Vehicles (SUVs) Sales in U.S.
5 4 3 2 1
Year
Sales (in Millions)
1991
0.9
1992
1.1
Vehicle Sales (Millions)
1993
1.4
1994
1.6
1995
1.7
1996
2.1
1997
2.4
1991 1993 1995 1997 1999 1992
1994 1996 1998 2000
x
1998
2.7
1999
3.2
Year
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Scatterplot - a coordinate graph of data points.
y
Trend appears linear.
5 4 3 2 1
Trend is increasing.
Vehicle Sales (Millions)
Positive correlation.
Predict the sales in 2001.
1991 1993 1995 1997 1999 1992
1994 1996 1998 2000
x
Year
19
Plot the data on the graph such that homework
time is on the y-axis and TV time is on the
x-axis..
Time Spent Watching TV
Time Spent on Homework
Student
Sam
30 min.
180 min.
Jon
45 min.
150 min.
Lara
120 min.
90 min.
Darren
240 min.
30 min.
Megan
90 min.
90 min.
Pia
150 min.
90 min.
Crystal
180 min.
90 min.
20
Plot the data on the graph such that homework
time is on the y-axis and TV time is on the
x-axis.
TV
Homework
240 210 180 150 120 90 60 30
30 min.
180 min.
45 min.
150 min.
Time on Homework
120 min.
90 min.
240 min.
30 min.
90 min.
120 min.
150 min.
120 min.
180 min.
90 min.
30 90 150 210 60
120 180 240
Time Watching TV
21
Describe the relationship between time spent
on homework and time spent watching TV.
Trend appears linear.
240 210 180 150 120 90 60 30
Trend is decreasing.
Time on Homework
30 90 150 210 60
120 180 240
Negative correlation.
Time Watching TV