November 6-9, Seattle, WA

Bad Reports: Fixing Their Mistakes

Roger NobleConsultant

LobsterPot Solutions

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My bad report

NSW Police reportJust an example, not really from the NSW Police Dept. (source data.gov.au)

Report is used to: • Track incident response times• Incident rates across divisions• Incident rates by offence

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Bad ReportDemo

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First Some Theory

What are we trying to communicate?

Remove non-data pixels and chartjunk

Increase data density

Use colour sparingly

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Data ink and non-data ink

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Chartjunk

= 38.7%

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Colour

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ThingsStuffBitsBobsWhatsitWidgetWhirlyBytesPickleTomato

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Data-Ink Ratio

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Ink used to present the data

Total ink used

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Process for continual improvement

1. Identify non-data pixelsa. Can it be removed?b. Can it be deemphasised?

2. Identify data pixelsa. Is it meaningful?b. Can it be emphasised?

3. Repeat

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Let’s fix it!Demo

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Charts

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Charts

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Charts

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Data types

Dimensions• Nominal Location• Ordinal Days of week• Interval Time

Measures• Additive Sales amount• Non-additive Temperature

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Data types - Charting

Dimensions Measures Nominal Ordinal Interval Additive Non-

additiveMeasuresAdditive Non-additive

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Charting – Line vs Bar

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Nominal

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Charting – Line vs Bar

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Nominal

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Charting – Line vs Bar

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Interval

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Charting – Line vs Bar

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Interval

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Let’s fix it!Demo

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Tables

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Tables

Remove unnecessary colour and gridlines

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Tables

Remove gridlines and unnecessary colour

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Tables

Add lines and emphasis where necessary

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Tables

Add white space to aid with reading

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Tables

Add white space to aid with readingWhite space allows the eye to easily scan down columns and across rows

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Indicators

Be optimisticadd indications only for exceptions

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Indicators

Be optimisticadd indications only for exceptions

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Let’s fix it!Demo

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Problems with Pie charts

Requires mental conversion from size/angle to percentage.

Works well when values are close to 25% and 50% (90o and 180o)

1234

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Problems with Pie charts

Distortion from perspectiveSlices that are closer appear larger than they are

1234

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Problems with Pie charts

Actual values can be listed in a smaller space (higher data-ink ratio)

1234 =

1. 32% (40)2. 24% (30)3. 20% (25)4. 24% (30)

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Problems with Pie charts

Patterns are harder to perceive

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0 2 4 6 8 10 120

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VS

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Area based charts

Area is difficult to quantifyBubbles must be sized by area not diameter (or radius or circumference)

IncorrectSized by diameter

CorrectSized by area

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N 2N

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What else is bad?

Size can be perceived differently based on surroundings

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Let’s fix it!Demo

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Summary

Identify key information

Improve the data-ink ratio (remove chartjunk)

Use whitespace to aid in scanning rows and columns

Be optimistic with indicators

Only use area based charts when accuracy isn’t important

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Recommended Reading

Edward Tufte

Steven Few

Also: William S. Cleveland, Colin Ware, Nathan Yau and Benjamin Willers

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39November 6-9, Seattle, WA

Thank youfor attending this session and the 2012 PASS Summit in Seattle