WPC_300_Data_Visualization_Principle_2.pdf.pdf

WPC 300

Problem Solving and Actionable Analytics

Data Visualization

Kevin Hong

[email protected]

http://kevinhong.me/

Some basic principles (adapted from Tufte 2009)

•The chart should tell a story

•The chart should have graphical integrity

•The chart should minimize graphical

complexity

Tufte’s fundamental principle:

Above all else show the data

Principle 2: The chart should have

graphical integrity

•Basically, it shouldn’t “lie” (mislead the reader)

•Tufte’s “Lie Factor”:

•𝐿𝑖𝑒 𝐹𝑎𝑐𝑡𝑜𝑟 = 𝑠𝑖𝑧𝑒 𝑜𝑓 𝑒𝑓𝑓𝑒𝑐𝑡 𝑠ℎ𝑜𝑤𝑛 𝑖𝑛 𝑔𝑟𝑎𝑝ℎ𝑖𝑐

𝑠𝑖𝑧𝑒 𝑜𝑓 𝑒𝑓𝑓𝑒𝑐𝑡 𝑖𝑛 𝑑𝑎𝑡𝑎

Should be ~ 1

< 1 = understated effect > 1 = exaggerated effect

Examples of the “lie factor”

𝐿𝐹 =5.3/0.6

27.5/18 =8.83

1.53 = 5.77

𝐿𝐹 =4280% (𝑐ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑣𝑜𝑙𝑢𝑚𝑒)

454% (𝑐ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑝𝑟𝑖𝑐𝑒) = 9.4

Reprinted from

Tufte (2009), p.

57 & p. 62

How about this?

http://20bits.com/articles/politics-and-tuftes-lie-factor/

The original graphic from Real

Clear Politics, 2008.

(Look at the y-axis)

The adjusted graphic.

Or this?

The original graphic from

Fox News, March 2014.

A different graphic, the next

day...

http://mediamatters.org/blog/2014/03/31/dishonest-fox-charts-obamacare-enrollment-editi/198679

Other tips to avoid “lying”

Adjust for

inflation

Make sure

the context

is presented

100

110

120

130

140

2003 2004 2005 2006 2007 2008 2009 2010

Year

Hypothetical Industries, Inc.

Revenue

Adjusted Revenue

350

360

370

380

390

400

410

2009 2010

Thefts per 100000 citizens

Hypothetical City Crime

125

175

225

275

325

375

425

2003 2004 2005 2006 2007 2008 2009 2010

Thefts per 100000 citizens

Hypothetical City Crime

vs.

Students also viewed