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
01/11/11 Misleading Graphs
Today’s Plan:-Warm-Up & Correct Homework-Misleading Graphs
Learning Target: I will describe misleading graphs.
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.
Explain why this graph is misleading.
The scale is so compressed that it’s hard to see any difference among the brands.
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.
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 $0.10 per minute.
Course 2
7-10 Misleading Graphs
Both line graphs show the high temperature Monday through Friday. Which graph could be misleading? Why?
Additional Example 1
Course 2
7-10 Misleading Graphs
The graph on the right could be misleading. It gives the impression of greater temperature change because the vertical axis does not begin at zero.
Check It Out: Example 1
Course 2
7-10 Misleading Graphs
Graph B could be misleading. The vertical axis does not begin with zero, so differences in scales appear greater.
Graph B
Which graph could be misleading? Why?
Pri
ce p
er m
eal
25
20
15
10
0Gino’s Village
GrillPasta City
City Diner
Graph A
30
25
20
15
10Gino’s Village
GrillPasta City
City Diner
Pri
ce p
er m
eal
Average Restaurant Meal Price
Explain how you could redraw the graph so it would not be misleading.
Additional Example 2A: Analyzing Misleading Graphs
Course 2
7-10 Misleading Graphs
Draw the entire vertical scale on the graph.
Additional Example 2B: Analyzing Misleading Graphs
Course 2
7-10 Misleading Graphs
Explain how you could redraw the graph so it would not be misleading.
Draw the vertical scale with equal spacing between marks so that the distance between 0 and 18,000 equals the distance between 18,000 and 36,000.
Explain how you could redraw the graph so it would not be misleading.
Check It Out: Example 2A
Mon Tue Wed Thu Fri
13 12 11 10
Taxicab Fares
Far
e ($
)
Course 2
7-10 Misleading Graphs
Draw the entire vertical scale on the graph. The vertical axis is broken, so differences in fare appear greater.
Explain how you could redraw the graph so it would not be misleading.
Check It Out: Example 2B
Course 2
7-10 Misleading Graphs
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
7-10 Misleading Graphs
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
Explain why each statistic is misleading.
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.
Explain why each statistic is misleading.
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 Target: I will describe misleading graphs.
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