top 5 data visualization errors

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TOP 5 DATA VISUALIZATION ERRORS

Professor Kristen Sosulski, Ed.DNew York University Stern School of Business@sosulski | [email protected] | kristensosulski.com

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Introduction• Building data visualizations is easy. • In fact, you can build beautiful geospatial, categorical,

statistical, relational, multivariate, and time series displays with little effort, as long the data is presented in the correct format.

• However, it’s always important to study and review the output of your visualizations; the default settings can result in errors of omission and poor scaling.

Copyright 2016 Kristen Sosulski [email protected] @sosulski kristensosulski.com

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Learn how to avoid errors made by data visualization

software.


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Top 5 errors made by software

Maps: Excluding AK

and HIPoor scaling Excluding the

data source

Using different shades for

bars

Encodings without

explanation


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ERROR 1

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What’s wrong with this map?


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Answer:

The map below shows the location of aviation incidents and accidents in the US. However, it only shows the 48 contiguous states.

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How do we correct this error?• When mapping data points on a geospatial display of

the United States, be sure to include all 50 states.

• To include Alaska and Hawaii on your map, simply take screenshots of the two states from your original visualization (you may have to zoom out or pan), and paste them near the west coast of the US.


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Corrected map by including AK and HI.

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ERROR 2

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What’s wrong with this chart?

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Answer:• The bars represent the number of TEUs by

year in China’s ports. The y-axis presents the data in thousands.

• The numbers on the scale are difficult to read such as 40200K.

• 40200K is simply, 40,200,000 or 40.2 million.


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How do we correct this error?• In this case, the y-axis should be set to the

highest denomination, which in this case in millions.

• I see this mistake often with Tableau generated charts. See the corrected chart on the next slide.


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Corrected the chart by setting the y-axis scale to millions.

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ERROR 3

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What’s missing from this chart?


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Answer:• Omitting a reference to the data source.

This makes it impossible to check the validity and integrity of the visual presentation.

• Also, the scale is also omitted on this chart.

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Corrected the chart by adding the data source.

Source: NYC Open Data: 311 Calls (2010-2015)Copyright 2016 Kristen Sosulski [email protected] @sosulski kristensosulski.com

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ERROR 4

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What’s confusing about this this chart?


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Answer:• There are there redundant encodings for the

categorical data.• The value of each bar is represented by both a

color and a number, in addition to the bar length.

• There is no extra information provided by the different colors used.


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How do we correct the error?• Remove the different colors or shading

within the same bar chart. • The label describing the bar should make

it clear enough what the bar represents..


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Corrected the chart by removing the different shades of green on the bars.


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ERROR 5

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What’s unclear about this map?


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Answer:• There is no description of what the colors, bubbles, and bubble

size signify in the chart.

• Bubble charts are used to display multivariate data. The size of a bubble represents a quantitative value such as population or quantity, while the color usually is a categorical variable such as region.

• The position of the bubble is the intersection of the x and y coordinates. In this case, it is the longitude and latitude.

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How can we fix this error?Simply include a legend to explain the color codes and sizes of your bubbles.


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Corrected the error by including a legend.

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Summary: 5 errors made by data visualization software.

Maps: Excluding AK

and HIPoor scaling Excluding the

data source

Using different shades for

bars

Encodings without

explanationCopyright 2016 Kristen Sosulski [email protected] @sosulski kristensosulski.com

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By checking for these five errors made by data visualization software, you’ll be on your way to creating data visualizations like a pro.


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Are there any other errors that you’ve come across in your data visualization work? Do you have any questions? Contact me on twitter @sosulski.

You can learn more on my blog at http://kristensosulski.com

Questions? Comments?


http://kristensosulski.com/

http://kristensosulski.com/

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Thank you!Professor Kristen Sosulski, Ed.DNew York University Stern School of Business

@sosulski | [email protected] | kristensosulski.com

top 5 data visualization errors

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