bad reports: fixing their mistakes
DESCRIPTION
Bad Reports: Fixing Their Mistakes. Roger Noble Consultant LobsterPot Solutions. My bad report. NSW Police report Just 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 - PowerPoint PPT PresentationTRANSCRIPT
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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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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What else is bad?
Size can be perceived differently based on surroundings
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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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Thank youfor attending this session and the 2012 PASS Summit in Seattle