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Why Worry About Graphics?

Why Worry About Graphics?. “Data graphics are mainly devices for showing the obvious to the ignorant” “They have to be alive , communicatively dynamic , decorated , and exaggerated ; otherwise all the dullards will fall asleep in the face of those boring statistics”

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Why Worry About Graphics?

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  1. Why Worry About Graphics? • “Data graphics are mainly devices for showing the obvious to the ignorant” • “They have to be alive, communicatively dynamic, decorated, and exaggerated; otherwise all the dullards will fall asleep in the face of those boring statistics” • Graphics are instruments for reasoning about quantitative information… They reveal data.” (Tufte 1983)

  2. Principles of Graphic Excellence • Graphical excellence….. • consists of complex ideas communicated with clarity, precision, and efficiency. • is that which gives to the viewer the greatest number of ideas in the shortest time with the least ink in the smallest space. • is nearly always multivariate (illuminating relationships between numerous variables) • requires telling the truth about the data

  3. Some Rules of Thumb • Graphic displays should….. • show the data • avoid distorting the data • induce the viewer to think about the substance of the graphic rather than the methodology, graphic design, or something else • make large amounts of data coherent • encourage the viewer to use the graphic as you intend, e.g. make comparisons • be closely integrated with statistical and verbal descriptions of the data • be as simple as possible

  4. Design Guidelines • To enhance visual quality: • use a properly chosen format • use words, numbers, and graphics together • display an accessible complexity of detail • have a story to tell about the data • produce technical details with care • avoid chartjunk

  5. Effective Communication • “You can communicate more effectively with tables, graphs, or charts, if your {information has} these characteristics” (Booth et al. 1995): • They include discrete elements (cases) that are well defined, well understood, and stable - persons, places, things, or concepts. • The discrete element is an ‘independent’ variable, that does not change in response to other variables. • The discrete elements are systematically related to quantities or qualities, called dependent variables, that do not change in response to external causes.

  6. Tabular Presentation • “An informative table supplements rather than duplicates - the text.” (APA 1994) • Tables “are the best way to show exact numerical values and are preferable to graphics for many small data sets {of about 20 numbers or less}.” (Tufte 1983)

  7. State of Florida Household Income, 1999 Taken from the US Census Bureau Website

  8. The Tabular Superhero: Supertables • Tables also work well when the data presentation requires many localized comparisons, i.e. a supertable • Supertables are large tables made up of many different component tables that summarize relationships across the same variable(s)

  9. Rules of Thumb for Good Tables • Tables need a comprehensive and descriptive title (Variable, Geography, Time) Bay County Percent Population by Race, 2000 • Right justify numbers in tables • Use commas to delineate thousands • Use numeric signs to signpost the table viewer (percent signs (%), dollar signs ($), etc.) • Always use the same number of decimal places • Use gridlines to separate table elements • Use italics and bold to identify column headings

  10. Variations in County Poverty Rates, 1999 “Good Table” Example --Good Title --Nice presentation --Numeric formatting --Bold, Italics --Gridlines --Sourcing Source: 2000 Census Poverty Rates “Bad Table” Example --Poor Title --Confusing presentation --No source

  11. Choosing Formats: Charts/Graphs • “Figures convey at a quick glance an overall pattern of results.” • They are especially useful in describing an interaction - or the lack thereof - and nonlinear relations.” (APA 1994)

  12. Bar Charts and Graphs • Bar charts / graphs (histograms) are typically used when the independent variables are categorical variables [Nominal Variables] • They are also useful for showing changes over time as well (although line charts are often a better choice to show these relationships).

  13. Taken from the Tallahassee Statistical Digest, 2001

  14. Pie Charts • Pie charts are used to illustrate percentages or proportions of a whole. They are par5ticularly useful in investigating discrete elements of: -Populations -Budgets • But “at best, they allow readers to see crude proportions among a few elements.” (Booth et al. 1995)

  15. Line Graphs • Scatter plots and line graphs are used to show the relation between two quantitative variables where there is a unique value of the dependent variable for any value of the independent variable • The independent variable is typically plotted on the x axis while the dependent variable is plotted on the y axis • Line graphs are especially effective at presenting data that vary continuously

  16. Source: US Census

  17. Complex Graphs: Combination Charts • There are times when you want to present two or more variables in the same chart. • Combination charts allow the user to combine two different variables in the same chart in order to illustrate the relationships between these variables. • The choice of presentation method is dictated by the variables and the nature of the relationship between the variables.

  18. Source: US Census Clustered Column Chart Example

  19. Source: Tallahassee 2003 CIP Clustered Bar Chart Example

  20. Stacked Column Chart Example

  21. Line-Column Chart Example

  22. Four Broad Principals of Data Presentation (from Myers) • Integration: Tables and graphics should be part of a “seamless information flow”. Text should refer to and direct readers towards these exhibits. • Speed and Efficiency of Communication: Exhibits should be clearly and simply presented, well-titled, and linked to the purpose of the report/memo; The goal is efficiency of communication. • Engagement in Depth: The longer the viewer spends with an exhibit, the more they should get out of it. “The goal is to create a richly informative exhibit that is dense with information, but open and accessible to the eye.” • Trustworthiness: Exhibits present factual information. They must be supported with appropriate sourcing and with all information presented correctly and understandably.

  23. Presentation Reminder for Tables and Charts 1) Give ALL tables and figures titles and numbers.2) No “Hanging Tables and Figures”: Refer to any and all tables in a report/memo.3) Source all Tables and Charts 4) Provide a good title for all Tables and Charts (Variable, Geography, Time) 5) If you want a reader to compare two charts, show them on the same page.6) If you want a reader to compare two charts, use similar colors, titles, labels, fonts, and so on. The only major difference should be the data.

  24. Misleading the Unwashed Masses • While very powerful, graphics are potentially dangerous because they can easily mislead decision makers and the public at large. • Because graphics are often slick and attractive elements, they can lead viewers to assume certain things about them: 1) That graphics are accurate (truthful) and that data used to make the graphics are accurate. 2) They are neutral (objective) data displays that do not present any point-of-view in their display.

  25. A Graphical Caveat • “A single map is but one of an indefinitely large number of maps that might be produced for the same situation or the same data.” Monmonier, How to Lie with Maps, p. 2 • The maker of a graphic (maps and chart, especially) has tremendous power over the product and the consumer. This power can be used to create effective, attractive graphics that competently and truthfully convey information or graphics that unfairly distort reality and (un)intentionally mislead the audience.

  26. Graphical Deceit? If you were running for Mayor in Capital City, which graphic would you use to illustrate your success?

  27. The St. Joe Perspective The Riverkeepers Perspective

  28. Extra Credit Assignment:Examples of Good/Bad Graphics • Students in the class can earn up to 10 points to be added to your lowest Assignment Grade by finding examples of the following: • Graphical Excellence (up to 5 points) • Graphical Mediocrity or Deceit (up to 5 points) • Find examples of graphical excellence or graphical mediocrity/deceit and write up a one paragraph statement as to why a given graphic meets represents such an example.

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