1. Section 2-5
“Bad Graphs”

2. Key Concept Some graphs are bad in the sense that they contain errors.
Some are bad because they are technically correct, but misleading.
It is important to develop the ability to recognize bad graphs and identify exactly how they are misleading.

3. Are these graphs the same?
Case One
Are these graphs the same?

4. (Changing Graphing Scales)
Nonzero Axis
(Changing Graphing Scales)
-misleading because one or both of the axes begin at some value other than zero, so that differences are exaggerated.

5. Changing Graph Scales
(Average Home Prices)
Example A:

6. Changing Graph Scales (Graduation Rates) Example B: Year 1999 2000
2001
2002
2003
Number of Graduates
140
180
200
210
160

7. Is anything misleading in this graph?
Case 2
(Pictographs)
Is anything misleading in this graph?

8. Pictographs
are drawings of objects. Three-dimensional objects - money bags, stacks of coins, army tanks (for army expenditures), people (for population sizes), barrels (for oil production), and houses (for home construction) are commonly used to depict data.

9. These drawings can create false impressions that distort the data.
Pictographs using areas and volumes can therefore be very misleading.
Example C: If you double each side of a square, the area does not merely double; it increases by a factor of four;
(Similarly, if you double each side of a cube, the volume does not merely double; it increases by a factor of eight.)

10. Example D:

11. Annual Incomes of Groups with Different Education Levels
Example E:
Bars have same width, too busy, too difficult to understand.

12. Annual Incomes of Groups with Different Education Levels
Example F:
Misleading. Depicts one-dimensional data with three-dimensional boxes. Last box is 64 times as large as first box, but income is only 4 times as large.

13. Annual Incomes of Groups with Different Education Levels
Example G:
Fair, objective, not affected by distracting features.

14. Case 3: Is anything wrong with this graph?

15. Researchers asked people to identify their 3 favorite pies – adds up to 300%

16. Misleading Statistical Statements:
1.) You are more likely to die on the toilet than to be eaten by a shark.
2.) The FBI's Uniform Crime Reports (UCR) shows arrests of juvenile females for assaults and violent crime from 1980 through 2003 rose from 20 percent to more than 30 percent of the total.

17. 2.) Continued:
This is a perfect example of needing more information. The reality was that actual girl violence wasn’t shown to go up but the prosecution of girls did. A girl is more likely to get arrested for the same type of fight in 2003 than in 1980.