Bell Quiz

Objectives Analyze how graphs can be misleading.

Misleading Data When displaying data, components such as the scale or labels can make a graph misleading.

Example 1 Identifying Misleading Line Graphs The Line graph shows the number of members of a health club each month since it opened. Explain why the graph is misleading. Solution: Because the scale does not start at zero, the membership appears to have increased much more than it actually did.

Lesson Practice The graph shows the number of miles a car traveled each year. Explain why the graph may be misleading. Solution: The vertical scale does not begin at 0. The title does not specify whether the car or the driver traveled all the miles.

Misleading Data Another characteristic that may create a misleading graph is the size of the increments in the scale.

Example 2 Identifying Misleading Bar Graphs A radio station conducted a survey of music preferences of listeners. The bar graph shows the results. Explain why the graph may be misleading. Solution: The large increments of the scale make the data values appear to be closer than they actually are.

Lesson Practice The graph below shows baking temperatures of various foods. Explain why the graph may be misleading Solution: The large increments make the temperatures appear to be closer than they actually are.

Example 3 Identifying Misleading Circle Graphs The circle graph shows the number of some types of sandwiches a deli sells in one day. Explain why the graph may be misleading Solution: The title does not specify that these were the only sandwiches the deli sold, and it may not represent all categories.

Lesson Practice The circle graph shows the number of some kinds of dogs that were sold by the pet store. Explain why the graph may be misleading. Solution: The title does not specify that these were the only dogs the pet shop sold and may not represent all breeds sold.

Example 4 Application: Television Prices a.Explain why the graph my be misleading. b.What conclusion might be made from the graph? Why might the store have created this graph? c.Make a graph of the sales data that is not misleading.

Example 4 Solution Application: Television Prices a.The large increments make the data values appear to be closer than they actually are. b.The graph seems to show that the prices have not increased much over the past five years. The store may want it to appear as though prices have not increased significantly, when in reality they have actually increased by almost 50% c. c.

Lesson Practice a.Explain why the graph my be misleading. b.What conclusion might be made from the graph? Why might the salesman have created this graph? c.Make a graph of the sales data that is not misleading.

Lesson Practice Solution a.The vertical axis has a broken scale, so it appears that the number of products sold throughout the year changed more than it actually did b.The salesman may want it to appear that his sales increased a large amount from the beginning of the year to the end. c.