Gary Klass Department of Politics and Government Illinois State University - PowerPoint PPT Presentation

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Gary Klass Department of Politics and Government Illinois State University
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Gary Klass Department of Politics and Government Illinois State University

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  1. Gary Klass Department of Politics and Government Illinois State University

  2. From last years’ conference: Moving Practitioners Beyond Descriptive StatisticsSaturday, October 18, 2008 8:30 a.m. - 12:30 p.m.Seminar Description: Statistical analysis is very important with regard to reports, projects, policy, and the general understanding of information `processed on a daily basis. Many people are intimidated by mathematics and statistics, which causes an overreliance on simple descriptive statistics such as means, standard deviations, rates, and percent changes. These simple descriptive statistics all have limitations, however. The primary goal of this presentation is to identify the limitations of descriptive statistics and explore more meaningful bivariate and multivariate analyses, such as z-scores, t-tests, ANOVA, and regression.Instructor:Jamie Price, PresidentSocialphenom, Inc.West Palm Beach, Florida

  3. Part I – Principles of Data Display Part II – Statistical Fallacies

  4. Data Presentation Standards“Graphical Excellence” -- Edward Tufte • well-designed presentation of data of substance, statistics and design • complex ideas communicated with clarity, precision and efficiency • the greatest number of ideas in the shortest time with the least ink in the smallest space.Best example: Baseball statistics

  5. % Change, Index Crime Rates, Florida Counties 2007-8

  6. % Change, Index Crime Rates, Florida Counties 1998-08

  7. Defense presentation at John Gotti trial:

  8. Great Britain: Fatalities and Serious Casualties

  9. Better Crime Reports • New Jersey • NYC (Bronx) Compstat • Florida websiteoffense data

  10. Data Presentation Principles • Show the data • Minimize the ink to data ratio • Sort by a meaningful variable • Tell the Truth -- Avoid data distortion • Tables and charts should be self-explanatory • Highlight Meaningful comparisons

  11. Show the Data

  12. The problems with that chart • Time goes right to left • Scaling distortion • Unnecessary 3-D ink • Better not to use different colors to measure the same thing. • Year to year changes are usually not important.

  13. A Ten-line Chart: Robbery Rates 10 largest Cities

  14. Robbery Rates, Ten Largest Cities, 1985-2007*BJS: Data Online

  15. Sort the Data! • By the most meaningful variable • The Alphabet is not the most meaningful variable • Time goes left to right

  16. Sort Data by the most important variable The Alphabet is not the most important variable

  17. Sorting data by least meaningful variable Also note: unnecessary decimal place

  18. Revised Chart: Self-reported Use of Powder Cocaine Over the Past 30 Days, 2003, 2007 % of Arresteess Reporting Use

  19. Alphabetical Sorting

  20. Revised chart

  21. Stacked bar: Upside down?

  22. Revised:Officers Assaulted in Florida, 1991-2008

  23. Time goes left to right

  24. Tell the Truth! • Avoid Data Distortion

  25. New York State Criminal Justice, 2008 Crimestat Report

  26. Illinois

  27. Note also: Top charts uses 12 numbers to represent 5 datapoints

  28. Minimize the ink-to-data ratio • Avoid all ChartJunk • Never use 3-D • Eliminate unnecessary lines

  29. ChartJunk: Junked Car

  30. Don’t use Pie Charts!!!!!!! • Never use Pie Charts • Never ever use 3-D Pie Charts • Never compare data across two pie charts • Beware of the Pie Chart’s friends: pyramids, cones, donuts and radars

  31. Better but not great…

  32. Two pie charts are worse than one

  33. Revised Chart:Parolee Employment Status, 2007-8

  34. Revised chart

  35. Simple Graphics Boxplots, Sparklines, and Dot - Plots the greatest number of ideas in the shortest time with the least ink in the smallest space.

  36. FBI\UCR Violent Crime Rates: New York City and 69 Largest Cities ( 2007 population > 250,000) [show outliers]

  37. Sparklines: "intense, simple, word size graphics” - Tufte

  38. Sparkline bars