Lesson 11.4: Scatter PlotsLesson 11.4: Scatter Plots

Standards: M7D1f & M7A3a & cObjective: To construct a scatter plot

and determine the relationship between two variables.

Scatter PlotScatter 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.

y

This vertical line is called the y-axis.

THE COORDINATE PLANETHE COORDINATE PLANE

This horizontal line is called the x-axis.

y

x-5-5 -4-4 -3-3 -2-2 -1-1 00 11 22 33 44 55

55

44

33

22

11

00

-1-1

-2-2

-3-3

-4-4

-5-5

THE COORDINATE PLANETHE COORDINATE PLANE

y

x-5-5 -4-4 -3-3 -2-2 -1-1 00 11 22 33 44 55

55

44

33

22

11

00

-1-1

-2-2

-3-3

-4-4

-5-5

The x-axis and y-axis separate the coordinate plane

into 4 parts.

This point in the middle of the x-axis and y-axis is called

the originorigin.

THE COORDINATE PLANETHE COORDINATE PLANE

THE COORDINATE PLANETHE COORDINATE PLANE

y

x

Quadrant II

-5-5 -4-4 -3-3 -2-2 -1-1 00 11 22 33 44 55

55

44

33

22

11

00

-1-1

-2-2

-3-3

-4-4

-5-5

Quadrant I

Quadrant III

These parts are called Quadrants.

Quadrant IV

y

x-5-5 -4-4 -3-3 -2-2 -1-1 00 11 22 33 44 55

55

44

33

22

11

00

-1-1

-2-2

-3-3

-4-4

-5-5

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.

( 1 , 3 )The FIRST number is called the X- coordinate.

THE COORDINATE PLANETHE COORDINATE PLANE

The SECOND number is called the Y- coordinate.

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)

Construct a scatter plot to show the relationship between the hours spent practicing shooting darts and the dart shooting score.

0

5

10

15

20

25

30

0 1 2 3 4 5 6

Practice Time (hrs)

Dar

t S

hoo

tin

g S

core

Practice Time versus Dart Shooting Time

Ordered pair to graph (x, y)

(1, 6)

(2, 8)

(3, 13)

(4, 20)

(5, 18)

(6, 27)

Positive CorrelationPositive 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.

Positive CorrelationPositive Correlation• If you look at the age of a child and the child’s 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

Negative CorrelationNegative 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.

Negative CorrelationNegative Correlation

• If you look at the age of your family’s 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

No CorrelationNo 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.

No CorrelationNo 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.

ScatterplotsWhich scatterplots below show a linear trend?

a) c) e)

b) d) f)

NegativeCorrelation

PositiveCorrelation

ConstantCorrelation

Year

Sport Utility Vehicles(SUVs) Sales in U.S.

Sales (in Millions)

19911992

199319941995

1996

19971998

1999

0.91.1

1.41.61.7

2.1

2.42.7

3.2

1991 1993 1995 1997 1999 1992 1994 1996 1998 2000

x

y

Year

Veh

icle

Sal

es (

Mil

lion

s)

5

4

3

2

1

Objective - To plot data points in the coordinate plane and interpret scatter

plots.

1991 1993 1995 1997 1999 1992 1994 1996 1998 2000

x

y

Year

Veh

icle

Sal

es (

Mil

lion

s)

5

4

3

2

1

Trend is increasing.

Scatterplot - a coordinate graph of data points.

Trend appears linear.

Positive correlation.

Year SUV Sales

Predict the sales in 2001.

Plot the data on the graph such that homework timeis on the y-axis and TV time is on the x-axis..

StudentTime SpentWatching TV

Time Spenton Homework

Sam

Jon

Lara

Darren

Megan

Pia

Crystal

30 min.

45 min.

120 min.

240 min.

90 min.

150 min.

180 min.

180 min.

150 min.

90 min.

30 min.

90 min.

90 min.

90 min.

Plot the data on the graph such that homework timeis on the y-axis and TV time is on the x-axis.

TV Homework

30 min.

45 min.

120 min.

240 min.

90 min.

150 min.

180 min.

180 min.

150 min.

90 min.

30 min.

120 min.

120 min.

90 min.

Time Watching TV

Tim

e on

Hom

ewor

k

30 90 150 210 60 120 180 240

240

210

180

150

120

90

60

30

Describe the relationship between time spent onhomework and time spent watching TV.

Time Watching TV

Tim

e on

Hom

ewor

k

30 90 150 210 60 120 180 240

240

210

180

150

120

90

60

30

Trend is decreasing.

Trend appears linear.

Negative correlation.

Time on TV Time on HW