Misleading Graphs and Statistics

Misleading Graphs and Statistics 4.6 Pre-Algebra

Warm Up 1.How many students say oranges are their favorite? 2. What is the least popular fruit? 3. How many students answered the survey? Use the graph for problems 1-3 40 kiwi 90

Learn to recognize misleading graphs and statistics.

Graphs and statistics are often used to persuade. Advertisers and others may accidentally or intentionally present information in a misleading way. For example, art is often used to make a graph more interesting, but it can distort the relationships in the data.

Example: Identifying Misleading Graphs Explain why each graph is misleading. A. The graph suggests that the stock will continue to increase through 2020, but there’s no way to foresee the future.

Example: Identifying Misleading Graphs Explain why each graph is misleading. B. 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.

Example: Identifying Misleading Graphs Explain why each graph is misleading. C. The scale is so compressed that it’s hard to see any difference among the brands.

Try This Explain why each graph is misleading. A. % of Return on Investment 60 50 The graph suggests that the rate of investment return will continue to increase, but there are no guarantees 40 30 20 10 0 1 2 3 4 5* 6* * projected

Try This Explain why each graph is misleading. Preferred Juice Flavors B. 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) 150 148 146 144 142 140 Grape Cherry Apple

Try This Explain why each graph is misleading. C. Drink Sales This graph is too compressed to see much difference between the brands indicating that they are fairly equal. 120 No data from 50 to 120 100 80 60 40 20 0 Brand X Brand Y Brand Z

Example: 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.

Example 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.

Try This Explain why each statistic is misleading. 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.

Try This Explain why each statistic is misleading. C. The total revenue for bathing suits sold in May at Worthman’s Florida stores is 250,000. The total revenue for bathing suits sold in May at Worthman’s North Dakota stores is 10,000. The states have different populations and climates.

Lesson Quiz: Part 1 Explain why each graph or statistic is misleading 1. Possible answer: The size of the trucks is larger than the size of the cars, so it looks like there are as many trucks as cars, although there are 6 cars and 4 trucks.

Lesson Quiz: Part 2 Explain why each graph or statistic is misleading 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.

Misleading Graphs and Statistics