1. Displaying Data in Graphs and charts

2. Challenger Disaster

3. Report of the Presidential Commission on the Space Shuttle Challenger Accident, 1986 (vol 1, p. 145)

4. How to Display Data (Badly) Showing the data (choosing the data) Showing the data (choosing the data) Showing data accurately Showing data accurately Showing data clearly Showing data clearly H Wainer(1984). “How to display data badly.” American Statistician 38(2):137-147. http://www.jstor.org/view/00031305/di020581/02p0048x/0

5. Showing Data

6. Showing data Edward Tufte Edward Tufte Data Density Index Data Density Index Chart Junk Chart Junk It does not make sense to use graphs to display very small amounts of data. It does not make sense to use graphs to display very small amounts of data. The human brain is quite capable of grasping up to three values. The human brain is quite capable of grasping up to three values.

7. Showing Data

8. Graphs are only as good as the data they display. No amount of creativity can produce a good graph from dubious data.

9. Showing Data

10. Showing Data Accurately Graphs should not provide a distorted picture of the values they portray. Distortion can be either deliberate or accidental. Common Distortions Use of 3 dimensional “effects” Use of linear scaling when using area or volume to represent values.

11. 3 dimensional effects

12. No 3D Effect

13. Linear Distortion Fact: 1973 dollar : $0.44 1958 dollar: $1 Dimensions 1958 dollar is less than twice the height and width of the 1973 dollar Area: 1958 dollar has 3x the area

14. No Distortion

15. Hiding Information

16. Not so hidden

17. Showing Data Clearly Graphs should be no more complex than the data which they portray Unnecessary complexity can be introduced by chartjunk irrelevant decoration color

18. Showing Data Clearly Age Structure of College Enrolment (1972- 1976) 4 variables 6 colors Weird perspective SPLIT AXIS American Education Magazine.

19. Showing Data Clearly

20. Tips for “Good” Graphs, Tables and Charts Tell the truth – don’t distort the data If the data is very simple, just use text Simplify If the “story” is simple, keep it simple. If the “story” is complex, make it look simpler “Keep it Simple” (for presentations)

21. A complex graph is sometimes the best way to tell a story

22. The Cognitive Style of PowerPoint (Edward Tufte) How Not to Use PowerPoint How Not to Use PowerPoint How Not to Use PowerPoint How Not to Use PowerPoint Bullet Points are bad Bullet Points are bad Style no substitute for content Style no substitute for content 40 words = 8 seconds of silent reading = very little actual content 40 words = 8 seconds of silent reading = very little actual content

23. Analytics According to Captain Kirk Analytics According to Captain Kirk PowerPoint does not provide enough detail for analysis PowerPoint does not provide enough detail for analysis One needs to look at all of the data to do a proper analysis One needs to look at all of the data to do a proper analysis

30. Clarification Simple