Presented to: By: Date: Federal Aviation Administration Effective Data Presentation Fernwood Avenue Middle School December 21, 2011 Ferne Friedman-Berg, Ph.D. Kenneth Allendoerfer, Ph.D.

2 Federal Aviation Administration Effective Data Presentation December 21, 2011 Introduction Good and bad data displays are a lot like good and bad writing Good graphical displays of data communicate ideas with: –Clarity –Precision –Efficiency Bad graphical displays: –Distort or obscure the data –Make it harder to understand or compare –Don’t effectively communicate the “take home” message of the graph.

3 Federal Aviation Administration Effective Data Presentation December 21, 2011 Complexity ≠ Good Graph

4 Federal Aviation Administration Effective Data Presentation December 21, 2011 Pretty ≠ Good

5 Federal Aviation Administration Effective Data Presentation December 21, 2011 Data Need to Make Sense What???????

6 Federal Aviation Administration Effective Data Presentation December 21, 2011 Bad Graphs: The Fundamentals Three fundamental elements of bad graphical displays –Data Ambiguity –Data Distortion –Data Distraction

7 Federal Aviation Administration Effective Data Presentation December 21, 2011 Recognizing Bad Graphs Graphs give an immediate visual image Why might a graph be bad: –bad because of errors –technically correct but misleading. It is important to recognize bad or misleading graphs in order to keep from getting the wrong impression.

8 Federal Aviation Administration Effective Data Presentation December 21, 2011 Bad Graphs – Errors Height represents the data. –Both the height and width increase proportionally. –This exaggerates differences viewer may look at the area, not height. Example: The incredible shrinking family doctor.

9 Federal Aviation Administration Effective Data Presentation December 21, 2011 Define and Summarize DO - tell us what your numbers represents –A Title –Axis Labels (e.g., distance, time) define scale (feet, seconds, etc.) –Legend DON’T - show individual subject data, unless you are creating a scatter plot. Show the chart to someone who doesn’t know your study and see what questions they ask. This can help you understand what is missing.

10 Federal Aviation Administration Effective Data Presentation December 21, 2011 Don’t Chart Individual Subjects Weights (pounds) of rowers on 2004 U.S. Men’s Olympic Rowing Team Individual data Weights (pounds) of rowers on 2004 U.S. Men’s Olympic Rowing Team Improved Graph

11 Federal Aviation Administration Effective Data Presentation December 21, 2011 Some DO’s & DON’TS of Good Graphing DO - Maximize the ratio of data to ink. DON’T - use extraneous lines DON’T – use 3-D DON’T - rotate the perspective.

12 Federal Aviation Administration Effective Data Presentation December 21, 2011 Chartjunk Anything that doesn’t NEED to be included in the chart. Watch your data-to-ink ratio. Data-to-ink ratio =data ink total ink

Hard to read font

14 Federal Aviation Administration Effective Data Presentation December 21, 2011 Data-to-Ink Ratio too low! How many people speak Spanish? Chartjunk

15 Federal Aviation Administration Effective Data Presentation December 21, 2011 Rotated Perspective & Extraneous Lines: When were the most singles sold? 1995 & 1997…but you wouldn’t know that from the first graph! Graph 1 Graph 2

16 Federal Aviation Administration Effective Data Presentation December 21, 2011 Another Rotated Perspective View that Distorts the Data

17 Federal Aviation Administration Effective Data Presentation December 21, 2011 Extraneous Lines: Can you see the data?

18 Federal Aviation Administration Effective Data Presentation December 21, 2011 What's Wrong With This One? 3-D Gone Wild The use of 3-D is unnecessary and confusing. What would be better? Colors Four different line types –e.g., Solid, Dashed, Dotted, Dash- dotted

19 Federal Aviation Administration Effective Data Presentation December 21, 2011 DON’T use inconsistent scaling –This makes differences look bigger than they actually are DON’T use inaccurate labeling –This can mislead the reader DON’T use a non-zero axis –It can be misleading if axis starts at a value other than zero. More DO’s & DON’TS of Good Graphing

20 Federal Aviation Administration Effective Data Presentation December 21, 2011 Inconsistent Scaling and Deceptive Labeling

21 Federal Aviation Administration Effective Data Presentation December 21, 2011 Inconsistent Scaling: What’s wrong with the x and y scales? 20 points 10 points

22 Federal Aviation Administration Effective Data Presentation December 21, 2011 What is your baseline? Use a reliable frame of reference –Confusion may be related to unexpected changes in scales. Non-zero Baseline Zero Baseline

23 Federal Aviation Administration Effective Data Presentation December 21, 2011 Lie Factor Lie Factor = size of effect shown in graphic size of effect in data Greater than 1.05% or less than.95% indicates substantial distortion, far beyond minor inaccuracies in plotting.

24 Federal Aviation Administration Effective Data Presentation December 21, 2011 NYT: Fuel economy “graph” Lie factor ≈ 14.8

25 Federal Aviation Administration Effective Data Presentation December 21, 2011 A more accurate representation

26 Federal Aviation Administration Effective Data Presentation December 21, 2011 What about this one? Map combines all three measures It is completely unreadable. –blended colors not clear More effective presentations: –To show places with low to high levels of all three measures (reading, writing, and earnings), a single measure that combines your measures into a single color ranging from light to dark would work better. –To show the individual measures, three separate maps works best.

27 Federal Aviation Administration Effective Data Presentation December 21, 2011 Another “DON’T” This graph has a flashy background and bright colors, however, it’s not very good. Why not? What is it describing? –Crime rates? –NO! It actually describes the percentage change in violent crime rates. –New York at 20% of its 1990 crime rate could still be more violent than Philadelphia at over 100% of its 1990 crime rate. –If you want to know how dangerous these cities really are, you’ll have to look elsewhere.

28 Federal Aviation Administration Effective Data Presentation December 21, 2011 Statistics for Science Fairs What difference is meaningful? When is it scientifically valid to say that two numbers are different? –Is an 80 on a test different than an 81? How much would you pay for a new teaching method for a gain of one point? –If you are trying to say two numbers are different you might want statistics to back up what you say.

29 Federal Aviation Administration Effective Data Presentation December 21, 2011 Too Many Data Labels

30 Federal Aviation Administration Effective Data Presentation December 21, 2011 Not Enough Labeling

31 Federal Aviation Administration Effective Data Presentation December 21, 2011 Summary: Principles of Good Graphs Always include labels and legends Always indicate units of measurement Let the data speak for themselves Avoid fancy 3D graphs and visual effects that hide the message in the data Avoid double Y-axes Watch for the “lie factor” – the perceived change vs. the actual change (e.g., area vs. length) Think carefully about the choice of scales Make sure the data are accurate Use consistent scaling Organize by the most important features of the data

32 Federal Aviation Administration Effective Data Presentation December 21, 2011 Same Data, Different Scales

33 Federal Aviation Administration Effective Data Presentation December 21, 2011 Tufte Principles Show Data Focus on Content First, Not Graphic Production Do Not Distort Encourage the Eye to Compare Different Pieces of Data Closely Integrate Statistical and Verbal Descriptions

34 Federal Aviation Administration Effective Data Presentation December 21, 2011 Line Graph –Best when x-axis is a quantitative or ordered variable –Variables have contiguous values –Use familiar/conventional ordering Don’t put sophomores before freshman Bar Graph –Compares relative point values Scatter Plot –Conveys overall impression of relationship between two variables Pie Chart –Emphasizes differences in proportion among a few numbers Types of Charts and Graphs

35 Federal Aviation Administration Effective Data Presentation December 21, 2011 Scatterplot Example

36 Federal Aviation Administration Effective Data Presentation December 21, 2011 Pie Chart Example

37 Federal Aviation Administration Effective Data Presentation December 21, 2011 Bar charts Best for comparing different things during the same time period Neither the bars nor the axis should be interrupted Axis should usually include zero (some exceptions) Again - avoid 3-D effects, can be misleading

38 Federal Aviation Administration Effective Data Presentation December 21, 2011 Bar Charts: Bad Use of Shading Emphasis on one bar

39 Federal Aviation Administration Effective Data Presentation December 21, 2011 Bar Chart

40 Federal Aviation Administration Effective Data Presentation December 21, 2011 Line graphs Best for showing change over time Can indicate trends Use a different color and symbol for each line Avoid too many lines

41 Federal Aviation Administration Effective Data Presentation December 21, 2011 Line Graph

Figure 1: Percent of elders in intergenerational families Too many lines! Use color wisely!

Percent of Persons Aged 65+ Residing with their Own Children aged 18+: United States Labeling: Title Height/width should be about 3:4 (same as old- fashioned TV Labeling: lines

44 Federal Aviation Administration Effective Data Presentation December 21, 2011 Minard's Napoleon's March to Moscow

45 Federal Aviation Administration Effective Data Presentation December 21, 2011 Contact Information Dr. Ferne Friedman-Berg, Ph.D. Dr. Kenneth Allendoerfer, Ph.D. Engineering Research Psychologists FAA Aviation Research Division Human Factors Branch, ANG-E25 William J. Hughes Technical Center, Bldg. 28. Atlantic City International Airport, NJ Fax: (609)

46 Federal Aviation Administration Effective Data Presentation December 21, 2011 Supplementary Material

47 Federal Aviation Administration Effective Data Presentation December 21, 2011 References infographic-forever/ infographic-forever/ Boyd, J.P., Scientific Visualization and Information Architecture Course: Chapter 1. Downloaded from Huff, D., (1991). How to Lie with Statistics. Tufte, E., (1983). The Visual Display of Quantitative Information.

48 Federal Aviation Administration Effective Data Presentation December 21, 2011 Online Practice BBC online practice entingdata2rev5.shtml entingdata2rev5.shtml Glencoe online tools bin/msgQuiz.php4?isbn= &chapter=4&lesson=8 bin/msgQuiz.php4?isbn= &chapter=4&lesson=8 Excel Activities: sleading_graphs.html sleading_graphs.html References

49 Federal Aviation Administration Effective Data Presentation December 21, 2011 On-Line Charting Tools (some are free) 18/charts-and-graphs-modern-solutions/

50 Federal Aviation Administration Effective Data Presentation December 21, 2011 On-Line Statistics Resources and Applets tat/default.htmhttp:// tat/default.htm

51 Federal Aviation Administration Effective Data Presentation December 21, 2011 Choosing a Statistical Test