1. 9.4 Part 2: Misleading graphs
Essential Question:
How can you recognize a Misleading Data Display?

2. Type #1: A Break in the Vertical Axis (zigzag)
Both line graphs show the high temperature Monday through Friday. Which graph could be misleading? Why?
The graph at right could be misleading. It gives the impression of greater temperature change because the vertical axis does not begin at zero.

3. Average Restaurant Meal Price
Type #2: Vertical Axis does Not Start at Zero
Graph B
Which graph could be misleading? Why?
Price per meal 20 15 10 5
Gino’s
Village Grill
Pasta City
City Diner
Graph A 25
Average Restaurant Meal Price
Graph B could be misleading. The vertical axis does not begin at zero, so differences in scales appear greater.

4. Type #3: Intervals in Histogram Not Constant
Why is this a misleading graph? 20 16 12 8 4
1–2
3–6
7–9
Hours of Television Watched
Frequency
Hours

5. Type #4: Icons in Pictograph Not Same Size

6. Type #5: Vertical Axis- Not Same Spacing between Marks
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.

7. Type #6: Bars on Graph Not Same Width
Explain how you could redraw the graph so it would not be misleading.

8. Type #7: Size of Sectors Not Proportional to Percents
Explain how you could redraw the graph so it would not be misleading.

9. On Your Own Explain why each graph could be misleading. 1.
The vertical scale on the graph is not small enough to show the changes because it doesn’t start at 0.

10. Widths of bars are not the same. 2.
Explain why this graph could be misleading.
Widths of bars are not the same.
Intervals of histogram are not consistent

11. B. The vertical scale is not small enough to see differences.
3. Explain why the graph could be misleading.
A. The vertical axis is broken, so it looks like fewer people like each type of drink.
B. The vertical scale is not small enough to see differences.
C. The intervals are not equal to compare the frequencies.
D. The vertical axis does not begin with zero.

12. 4. Explain why the graph could 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.