6th Grade Math Textbook, Fundamentals

 &KDSWHU

8-11

Value (thousands)

Mileage (thousands)

20 40 60 80 100 120 140 160 180 200

20

18

16

14

12

10

8

6

4

2

Vehicle Resale Value

The numbers for one

data set increase as the

numbers for the other

data set increase.

The numbers for one

data set decrease as the

numbers for the other

data set increase.

There is no pattern in

the way the numbers

for the data sets

increase or decrease.

Positive Correlation Negative Correlation No Correlation

Scatter Plots

Objective To use a coordinate plane to make a scatter plot• To read scatter plots

• To determine the line of best fit• To identify the type of correlation found in the data

Car dealers take many factors into account to
determine how much money to give customers on
the trade-in value of their vehicles. Mileage is one
of the factors. How can you use the data from the
table to show the correlation between the number
of miles a car has been driven and the resale value
of the vehicle?

To use the data to show the correlation (relationship)

between the number of miles a car has been driven

and its resale value, you can make a scatter plot.

A is a graph that compares two related

sets of data on a coordinate plane. Each point on a

scatter plot represents a pair of values.

To make a scatter plot:

Decide on a title for the graph.

Draw a vertical and a horizontal axis.

Choose a scale for each axis, using a range

and intervals that will fit the data.

Use the horizontal axis for the mileage scale

and the vertical axis for the values scale.

Plot a point for each pair of numbers in

the table.

The points show how the values of the vehicles

decrease as the number of miles increases.

In any scatter plot, the data displayed can be

described in three ways.

scatter plot

Mileage

(thousands)

Value

(thousands)

20 18

30 16

40 15

50 14

60 12

80 10

100 9

110 8

120 6

140 4

150 2

Data slopes

downward from

left to right.