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6-8 Misleading Graphs6-8 Misleading Graphs

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Warm UpWarm Up

Lesson PresentationLesson Presentation

Problem of the DayProblem of the Day

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6-8 Misleading Graphs

Warm UpUse 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?

2. What is the mode?

3. What is the range?

36

none

33

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6-8 Misleading Graphs

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

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6-8 Misleading Graphs

Learn to recognize misleading graphs.

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6-8 Misleading Graphs

Additional Example 1A: Misleading Bar Graphs

Why is this bar graph misleading?

Because the lower part of the vertical axis is missing, the differences in prices are exaggerated.

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6-8 Misleading Graphs

Additional Example 1B: Misleading Bar Graphs

What might people believe from the misleading graph?

People might believe that Cars B and C cost 1 to 2

times as much as Car A. In reality, Cars B and C are only a few thousand dollars more than Car A.

12__ 1

2__

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6-8 Misleading Graphs

Check It Out: Example 1A

Why is this bar graph misleading?

The vertical axis begins at 530 rather than 0.

600

550540530

580570560

Dollars

Money Raised

4th graders 5th graders 6th graders

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6-8 Misleading Graphs

Check It Out: Example 1B

What might people believe from the misleading graph?

That the 5th graders have raised twice as much money as the 4th graders.

600

550540530

580570560

Dollars

Money Raised

4th graders 5th graders 6th graders

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6-8 Misleading Graphs

Additional Example 2A: Misleading Line Graphs

Why are these graphs misleading?

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°.

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6-8 Misleading Graphs

Additional Example 2B: Misleading Line Graphs

What might people believe from these misleading graphs?

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.

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6-8 Misleading Graphs

Additional Example 2C: Misleading Line Graphs

Why is this line graph misleading?

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

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6-8 Misleading Graphs

Check It Out: Example 2A

Why are these graphs misleading?

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°.

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Week Week

Tem

pera

ture

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Tem

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ture

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September November

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6-8 Misleading Graphs

Check It Out: Example 2B

What might people believe from these misleading graphs?

People might believe that the temperatures in September were about the same as the temperatures in November. In reality, the temperatures in September were about 20 degrees higher.

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September November

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6-8 Misleading Graphs

Check It Out: Example 2C

Why is this line graph misleading?

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

0

50

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70

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1985 1990 1995 2000

Stock prices

Year

Pri

ce o

f st

ock

($)

Corp. C

Corp. D

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6-8 Misleading Graphs

Lesson Quiz

1. Why might this line graph be misleading?

2. What might people believe from the graph?

Possible answer: that there were hardly any visitors on Monday

The scale does not start at zero.