01/11/11 Misleading Graphs Today’s Plan: -Warm-Up & Correct Homework -Misleading Graphs Learning...

01/11/11 Misleading Graphs

Today’s Plan:-Warm-Up & Correct Homework-Misleading Graphs

Learning Target: I will describe misleading graphs.

Explain why this graph is misleading.

The graph suggests that the stock will continue to increase through 2020, but there’s no way to foresee the future.

Correct Homework

worksheet




For example, art is often used to make a graph more interesting, but it can distort the relationships in the data.

Graphs and statistics are often used to persuade. Advertisers and others may accidentally or intentionally present information in a misleading way.


The scale is so compressed that it’s hard to see any difference among the brands.





Because the scale leaves out 0 to 100, the bar heights make it appear that the sixth grade sold about three times as many tickets as either of the other two grades. In fact, the sixth grade sold only about 20% more.

B.

Try This: Example 1A

Explain why each graph is misleading.A.

0

10

20

30

40

50

60

1 2 3 4 5* 6** projected

% of Return on Investment

The graph suggests that the rate of investment return will continue to increase, but there are no guarantees

Try This: Example 1C

Explain why each graph is misleading.

C.

0

20

40

60

80

100

120

Brand X Brand Y Brand Z

Drink Sales This graph is too compressed to see much difference between the brands indicating that they are fairly equal.

No data from 50 to 120

Try This: Example 1B

Explain why each graph is misleading.

B.

140

142

144

146

148

150Preferred Juice Flavors

Grape Cherry Apple

The graph appears to indicate that significantly more people prefer grape drink over the others when in fact there is a small margin of difference. (0 to 140 is not graphed)

A data display that distorts information in order to persuade can be misleading.

An axis in a graph can be “broken” to make the graph easier to read. However, a broken axis can also be misleading.

In the graph at right, the cost per minute for service with Company B looks like it is twice as much as the cost for service with Company A. In fact, the difference is only $0.10 per minute.

Course 2

7-10 Misleading Graphs

Both line graphs show the high temperature Monday through Friday. Which graph could be misleading? Why?

Additional Example 1

Course 2


The graph on the right could be misleading. It gives the impression of greater temperature change because the vertical axis does not begin at zero.

Check It Out: Example 1

Course 2


Graph B could be misleading. The vertical axis does not begin with zero, so differences in scales appear greater.

Graph B

Which graph could be misleading? Why?

Pri

ce p

er m

eal

25

20

15

10

0Gino’s Village

GrillPasta City

City Diner

Graph A

30

25

20

15

10Gino’s Village

GrillPasta City

City Diner

Pri

ce p

er m

eal

Average Restaurant Meal Price

Explain how you could redraw the graph so it would not be misleading.

Additional Example 2A: Analyzing Misleading Graphs

Course 2


Draw the entire vertical scale on the graph.

Additional Example 2B: Analyzing Misleading Graphs

Course 2



Draw the vertical scale with equal spacing between marks so that the distance between 0 and 18,000 equals the distance between 18,000 and 36,000.


Check It Out: Example 2A

Mon Tue Wed Thu Fri

13 12 11 10

Taxicab Fares

Far

e ($

)

Course 2


Draw the entire vertical scale on the graph. The vertical axis is broken, so differences in fare appear greater.


Check It Out: Example 2B

Course 2


Water Consumed

48

40

32

24

16Mark Frank Mila Yvonne

Oun

ces

of W

ater

Draw the entire vertical scale on the graph. The vertical axis does not start at zero so differences in water consumed seem greater.

Lesson Quiz

Explain why each graph could be misleading and why.

The vertical scale on the graph is not small enough to show the changes.

Course 2


The scale does not start at 0, so it looks like fewer people like each type of animal.

1. 2.

Additional Example 2: Identifying Misleading Graphs

Explain why each statistic is misleading.

A. Sam scored 43 goals for his soccer team during the season, and Jacob scored only 2.

Although Jacob scored only 2 goals, he may have played most of his time on defense.

B. Four out of five dentists surveyed preferred UltraClean toothpaste.

This statement does not give the sample size or state what UltraClean toothpaste was compared with.

Additional Example 2 Continued


C. Shopping at Save-a-Lot can save you up to $100 a month!

The words save up to $100 mean that the maximum you can save is $100, but there is no guarantee that you will save that amount.


Try This: Example 2A & 2B

A. Four out of five breeders recommend Pet Blend dog food for a healthier coat.

This statement does not give the sample size or state what Science Blend dog food was compared with.

B. Fruity Squares makes the cereal 100% more fun.

You cannot measure how much fun Fruity Squares makes the cereal.

2. A budget area of a used-car lot has five cars on it, with prices of $4200, $4700, $4900, $5200, and $900 (a wrecked one). The car ad in the local paper reads “Average priced car on budget lot is $3980.”

The wrecked car’s price brings the average down. Without using the price of the wrecked car, the average price would be $4750.

Explain why each graph or statistic is misleading

Assignment: Problems off the screen

Homework:

Find one misleading statistic or graph in a newspaper, magazine, or online. Print it or write down the data and source. Write one sentence telling how it is misleading.




01/11/11 Misleading Graphs Today’s Plan: -Warm-Up & Correct Homework -Misleading Graphs Learning...

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