A Consumer’s Guide to Understanding Data - Data Fluency: Empowering Your Organization with Effective Data Communication - page 69

from raw data and examines some common charts to help you begin to find
meaning. In doing so, you see the importance of recognizing the “unexpected”
and contextualizing data through comparison.
Data visualization helps you see results and easily compare those results to
your expectations. Data that matches your expectations can help you under-
stand that they are on the right path and encourage you to do more of the
same. Results that are unexpected, however, will spur people to action. You
want to know: Does the world work the way you think it does? Or does the
data show you something that challenges assumptions of expected results?
Data visualizations are designed to emphasize patterns and deviations in
data. In fact, each specific chart type is well suited to highlighting particular
forms of insight.
A skilled author of data products will choose the right visualization to empha-
size a message. The data, chart, and supporting descriptions should work in
harmony to point out what is interesting. The reader simply goes along for
the ride.
Unfortunately, many data products end up a muddled mess of chart choices,
obscure labeling, and arbitrary layout. The producer has passed responsibil-
ity to the audience to find the meaning. Chapter 5, “Data Authors: Skilled
Designers of Data Presentations,” discusses the responsibilities of the data
product author to build a “guided safari” for readers.
Here is a quick tour of common charts to show you how they help you spot
the unexpected and use comparisons to find insights.
Unexpected Distributions
Pie charts are designed to show how something breaks into its constituent
pieces. The slices add up to the whole, and the volume of each slice indicates
its piece of the pie. (The obvious and tasty real-world analogy helps account
for the popularity of pie charts in the face of withering criticism by data visu-
alization experts.) The primary insight offered in a pie chart comes from slices
that are smaller or larger than you would expect. Readers must imagine what
they would expect the pie chart to look like and then find the differences.
In this pie chart (Figure 4-16), readers might be surprised to find that confec-
tions are nearly one-half their diet by volume. That's not healthy eating.