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```							 6-8 Misleading Graphs

Warm Up
Problem of the Day
Lesson Presentation

Course
Course 1 1

Warm Up
Use the data below to answer each
question.
20 21 23 24 27 33 34 35 36
38 40 41 42 43 46 52 53

1. What is the median? 36
2. What is the mode?   none
3. What is the range?   33

Course 1

Problem of the Day
Nine students in a group found that
their mean score was 86 for the first
math test. On the next test, each
student in the group scored 7 points
higher than on the first test. What was
their mean score for the two tests?
89.5

Course 1

Course 1

Why is this bar graph misleading?
Because the lower part of the vertical axis is
missing, the differences in prices are
exaggerated.

Course 1

What might people believe from the
1
__      1
__
People might believe that Cars B and C cost 1 to 2
2       2
times as much as Car A. In reality, Cars B and C are
only a few thousand dollars more than Car A.

Course 1
Check It Out: Example 1A
Money Raised
600
580
570
Dollars

560
550
540
530

Why is this bar graph misleading?
The vertical axis begins at 530 rather than 0.

Course 1
Check It Out: Example 1B
Money Raised
600
580
570
Dollars

560
550
540
530

What might people believe from the
That the 5th graders have raised twice as
much money as the 4th graders.

Course 1

If you look at the scale for each graph, you will
notice that the April graph goes from 54° to 66°
and the May graph goes from 68° to 80°.
Course 1

What might people believe from these
People might believe that the temperatures in May were
about the same as the temperatures in April. In reality, the
temperatures in April were about 15 degrees lower.
Course 1

Why is this line graph misleading?

The scale goes from \$0 to \$80, and then
increases by \$5.

Course 1
Check It Out: Example 2A
September                 November
Temperature (°F)

Temperature (°F)
90                                              70
80
70                                              60
60                                              50
50                                              40
40
30
30
20                                              20
10                                              10
0                                              0

1      2     3   4                             1   2   3   4
Week                                         Week
If you look at the scale for each graph, you will
notice that the September Graph goes from
85° to 70° and the November graph goes from
65° to 50°.

Course 1
Check It Out: Example 2B
September                 November
Temperature (°F)

Temperature (°F)
90                                            70
80
70                                            60
60                                            50
50                                            40
40
30
30
20                                            20
10                                            10
0                                            0

1      2     3   4                            1   2   3   4
Week                                        Week
What might people believe from these
People might believe that the temperatures in
September were about the same as the temperatures in
November. In reality, the temperatures in September
Course 1
Check It Out: Example 2C

Stock prices      Corp. C
Price of stock (\$)   80
Corp. D
70
60
50
0
1985 1990 1995 2000
Year

Why is this line graph misleading?

The scale goes from \$0 to \$50, and then
increases by \$10.

Course 1
Lesson Quiz
1. Why might this line graph be misleading?

The scale does not start at zero.
2. What might people believe from the graph?
Possible answer: that there were hardly any
visitors on Monday
Course 1

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