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Effective Communication Through Graphs: The do's and don'ts.

Juan Paulo RamírezPPC Brown Bag Meeting

29 November 2007

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Overview

IntroductionDefinitionTables vs. graphsHistory of the graph designWhy do we care about graph designStructureExamplesDo we always need a graph?The do’s and don’tsRecommendationsResources

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Introduction

This presentation focuses on scientific graphic design rather than explaining how to create graphs using a specific application.

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Objective of the Presentation

Learn how to communicate data through graphs in an effective, simple and correct way.

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Motivation

Map design is highly related to graph design.

People will read your publication and you want to make a good impression.

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Definition of a graph

A graph is a visual representation of data that displays the relationship among variables, usually cast along x and y axes. (source: LabWrite Resources/ Glossary).

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Tables vs. Graphs

Why not display data on a table?

A “table” talks, but not very well on behalf of data. It takes more time to analyze a table than a graph.

To know more about how to read a table: Ehrenberg, A. (1986). Reading a Table: An Example. Appl.Statist, 35 (3): 237-244.

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Calls by Age and Gender Male Female Total Calls % of Calls

Age Unknown % 18 and Under -

19-25 1 2 3 15% 26-35 5 1 6 30% 36-45 1 1 2 10% 46-55 3 3 6 30% 56-60 3 - 3 15%

61 and Over - - - %

If you have data in a table, that’s an invitation to be more creative.

If you have data in a table, that’s an invitation to be more creative.

From tables to graphs

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History of Graph Designs

What was done during the pre-EXCEL era?

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William Playfair (1759 – 1823)

Inventor of the time-series line graph, the bar chart, and the pie chart. Writer on political economy.

Inventor of the time-series line graph, the bar chart, and the pie chart. Writer on political economy.

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Florence Nightingale

First woman to become a member of the Royal Statistical Society in 1858 and an honorary member of the American Statistical Association in 1874.

First woman to become a member of the Royal Statistical Society in 1858 and an honorary member of the American Statistical Association in 1874.

Provided data that led to hospital reforms.

Provided data that led to hospital reforms.

“Polar-area diagram“. “Coxcomb diagram”

Florence Nightingale (1820 – 1910)

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Who is the “guru” of graph design today?

"The Leonardo da Vinci of data." THE NEW YORK TIMES

Edward Tufte (1942)

The Visual Display of Quantitative Information. "Best 100 books of the 20th century.“ AMAZON.COM Envisioning InformationVisual Explanations: Images and Quantities, Evidence and NarrativeBeautiful Evidence

Visual and Statistical Thinking: Displays of Evidence for Making Decisions.Essay: The cognitive style of PowerPoint: Pitching out corrupts within

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Why do we care?

Why should we care about graph design?

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It may save lives

The gridline obscured a big problem and could have prevented the Challenger disaster (1986).

The gridline obscured a big problem and could have prevented the Challenger disaster (1986).

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Graph Animation

Lesson learned: Keep your graphs simple and meaningful.

Lesson learned: Keep your graphs simple and meaningful.

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Next time you are here

Think twice

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Excel Chart Wizard tool

Ask yourself: Do I really need these gridlines?

Ask yourself: Do I really need these gridlines?

What about the background?

If you really need the gridlines, decrease the thickness and the color intensity of them.

If you really need the gridlines, decrease the thickness and the color intensity of them.

What about the background?

Maybe you need to get rid of it.

What about the background?

Maybe you need to get rid of it.

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This is what you get in Adobe Illustrator

Where are the gridlines, and the background color?

Where are the gridlines, and the background color?

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And this is what you get using SPSS

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Grids for Kids

You will get grids even if you do not want them!

You will get grids even if you do not want them!

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Why do we need the gridlines?

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Calls by Age and Gender October 2007

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1

2

3

4

5

6

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AgeUnknown

18 andUnder

19-25 26-35 36-45 46-55 56-60 61 and Over

Male

Female

Total Calls

Tufte Style

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Pie Charts (Many do not like them)

Grand Slam Won by Selected Tennis Players(ATP Era)

Pete SamprasRoger FedererJ ohn McEnroeJ immy Connors

“A table is nearly always better than a dumb pie chart.”

E. Tufte: The Visual Display of Quantitative Information.

“A table is nearly always better than a dumb pie chart.”

E. Tufte: The Visual Display of Quantitative Information.

Percentage of Chart which Resembles Pac-man

Does not resemblePac-man

Resembles Pac-man

Source:http://w w w .usablemarkets.com/?p=47

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Graph design is about consistency

The key point in creating a graph or a set of them is to keep consistency with your graphs.Consistency is knowing the elements of a graph (its particular height, color, size) and applying them uniformly when you are creating a graph or a series of them.

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Title: 20 ptsSubtitle: 14 pts

Font type: Verdana

Legend: 12 pts.Data label: 10 pts

X-axis title: 14 pts

Y-a

xis

tit

le: 14 p

ts

What about this?

What about this?

X and Y-axis labels : 12 pts

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Adding dimension to your graph

This feature adds “volume” to the bars.

This feature adds “volume” to the bars.

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Some examples

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Missing the scale

Source: Smith, P., Peppler, D. & Rigby, K. (2004). Bullying in Schools. How Successful Can Interventions Be? UK: Cambridge University Press.

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Good graphs may win you a Nobel Prize!

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Would you make any changes to this graph?

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A very well designed graph!

Note the color for the small bar.

Note the color for the small bar.

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Another well designed graph!

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Do we always need a graph?Percentage by Gender

50%50%

Female

Male

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The do’s

Keep your graphs simple. Do not clutter them with elements that do not add clarity to your data.Make sure that your graphs are consistent in terms of graphic design (i.e., font type and font size, color background). Add titles to your X-Y axes and include the units.

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Your graph has to have a title! Keep the title short ~ 25 words. Also add some relevant information such as time period, place where the data was collected, etc.

Tip: If you have to number your graphs for a publication, keep the number outside of the graph, since likely this number will change and you will end up having to change the whole graph (in PDF format or Image format).

The do’s

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The do’s (cont’)

Make sure that you have chosen the right type of graph to display your data. Is the pie chart the best option to display your data? Does a bar chart show a better idea of your data? Consider different options.Use middle tones for backgrounds but enough to contrast with the data elements of your graphs.

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The don’ts

Do not add extra graphs into the main graph, unless it is absolutely necessary.A pretty graph does not mean that it is a good graph. Adding too many extraneous elements into the graph may kill the message. Keep it simple.

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Recommendations

Creating the right set of graphs is time consuming. Set aside some time when working on your data for graph design.

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Resources

Tufte, E. (2006). Beautiful Evidence. Cheshire, Conn. : Graphics Press. _______(2003). The Cognitive Style Of PowerPoint. Cheshire, Conn. : Graphics Press._______(1997). Visual Explanations : Images And Quantities, Evidence And Narrative. Cheshire, Conn. : Graphics Press._______(1994). Envisioning Information. Cheshire, Connecticut: Graphic Press._______(1983). The Visual Display of Quantitative Information. Cheshire, Conn. : Graphics Press.

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Gallery of Data Visualization. The Best and Worst of Statistical Graphicshttp://www.math.yorku.ca/SCS/Gallery/Kid’s Zone/ Graphs: http://nces.ed.gov/nceskids/createagraph/default.aspxPeriodic Table of Visualization Methods:http://www.visual-literacy.org/periodic_table/periodic_table.html

Resources