1. Data Presentation Adapted by Joanna Wolfe from Marianne W. Zawitz, Bureau of Justice Statistics, October 11, 2000 Presenting effective Tables and Figures

2. This presentation covers the principles of creating good technical graphs and tables. 1. Provide descriptive captions. 2. Consider your “story” and audience when presenting data. 3. Avoid non-data ink. 4. Be ethical: Persuade but do not deceive.

3. Always label tables and figures. Figure 2: Recurrence of Gastric ulcers for the year after successful healing with ranitidine alone or triple therapy plus ranitidine. No maintenance was given. Percent with Ulcer Recurrence Weeks

4. Graphs excel at emphasizing trends and relationships while tables display exact values in a small amount of space. Weeks Ranitidine alone Triple therapy 48%0% 820%5% 1642%10% 2460%10% Table 1: Recurrence of Gastric Ulcers by Therapy Type Fig 2: Recurrence of Gastric Ulcers by Therapy Type

5. Line graphs are good for communicating change over time.

6. Bar graphs are good for communicating differences between values.

7. Pie charts are good for simple messages.

8. Bureau of Justice Statistics Pie charts are bad for complex data or when precision matters. Which slice is biggest? Which is smallest? By how much?

9. Bar charts allow readers to visualize differences between variables. Which bar is biggest? Which is smallest? By how much?

10. A21 B19 C18 D14 E12 F 9 G 7 Tables allow readers to see EXACT differences between variables and exact values. Which value is biggest? Which is smallest? By how much?

11. The visualization expert Edward Tufte says "the only thing worse than a pie chart is two pie charts." Which military branch grew the most between 1990 and 1998?

12. Bar charts simplify comparisons. Which military branch grew the most between 1990 and 1998?

13. A21 B19 C18 D14 E12 F 9 G 7 Which visualization is best for a technical audience?

14. Summary so far: Always supplement tables and figures with text: label axes and provide an informative caption. Use bar charts or tables to compare values. Use line graphs to show trends. Use tables when exact values are important. Only use pie charts for simple data and non- technical audiences.

15. Strive for simple designs that show the data. Avoid non-data ink Avoid non-data ink. Avoid 3D.

16. 3D charts add non-data ink and are more difficult to read than 2D charts. Is 1987 above or below 60 million? What about 1988? 1990?

17. Hidden data is a common problem with 3D presentations of 2D data Bureau of Justice Statistics

18. A simple line chart in 2 dimensions avoids hiding data West South Northeast Midwest Bureau of Justice Statistics

19. The purpose of a chart is to convey data so avoid non-data ink The purpose of a chart is to convey data so avoid non-data ink. Grids Ticks Frames Anything that does not convey data Bureau of Justice Statistics

20. 13-14 15 16 17 18 years old Age of offender Bureau of Justice Statistics Excess tick marks can make charts hard to read.

21. 13-14 15 16 17 18 years old Age of offender Bureau of Justice Statistics Removing tick marks make trends easier to see.

22. Implementation Before implementation After implementation Average vehicle speed45.5 mph45.7 mph Standard deviations in vehicle speed 9.4 mph 7.2 mph ImplementationBeforeAfter Average vehicle speed45.5 mph45.7 mph Standard deviations in vehicle speed 9.4 mph 7.2 mph Tables also benefit from minimizing non-data ink.

23. CompressorEfficiency score LZOP1 PAR1 PKZIP1 JAR.99 WINACE.98 WINZIP.97 STUFFIT.90 DEEPFREEZE.91 HUFFMANCE.91 OPAQUE.71 BLINK.58 Tables also benefit from minimizing non-data ink. CompressorEfficiency score LZOP1 PAR1 PKZIP1 JAR.99 WINACE.98 WINZIP.97 STUFFIT.90 DEEPFREEZE.91 HUFFMANCE.91 OPAQUE.71 BLINK.58

24. Criminal history of detained vs. released felony defendants, 1990 Prior criminal history Arrest Any conviction Felony conviction Violent felony conviction Avoid hatched fill patterns, which are hard to look at.

25. Stacked bars are also confusing.

26. Bureau of Justice Statistics "Simplicity of design and complexity of data" Edward R. Tufte