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3. There are sound principles for the display of quantitative infor-
mation. Perhaps the greatest theorist in the quantitative arena is Edward
Tufte. He has written a number of books and articles on the subject and
draws huge audiences worldwide when he speaks. Tufte virtually
founded the field of analytical design—the field that studies how best to
represent information—especially quantitative information. He has de-
veloped a number of principles over the years.
4. However,
in his latest book, Beautiful Evidence, published in
2006, he organized the principles under six major headings:
a. Show comparisons, contrasts, differences.
Comparisons inform
and invite reflection by the reader. For example, showing the growth
rate of platforms using the Mac iOS vs. other smartphone operating
systems helps show if the market is growing or shrinking.
b.
Show causality, mechanism, explanation, systematic structure.
Sometimes the data clearly suggest a cause or lack of a cause. For ex-
ample, many predicted a drop in iPhone 4 sales after news that the an-
tenna dropped calls when held in a certain way. But the predicted sales
drop was not borne out by the data and the product launch was wildly
successful.
c. Show multivariate data. That is show more than one or two vari-
ables. The more variables graphed, the greater the chance of providing
a clear causal explanation. For example, better
to show sales of paid
apps and free apps per platform.
d. Completely integrate words, numbers, images, diagrams. Tufte
sometimes calls this “whatever it takes.” Annotate your graph if that
helps explain the data. For example, on a time series you should label
key events.
e. Thoroughly describe the evidence. Provide a detailed title, indi-
cate the authors and sponsors,
document the data sources, show com-
plete measurement scales, point out relevant issues. For example, al-
ways show your data sources and list your name as a author. If the data
only holds under certain conditions, then state what those are.
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f. Analytical presentations ultimately
stand or fall depending on
the quality, relevance, and integrity of their content. This may be the
most important principle of all. If your content is bad then nothing will
save it. Try to tell the truth at all costs.
5. Most of the graph design guidelines come from Edward Tufte’s
principles of analytical design. These principles require refining the
graph after Excel has applied its default settings. Though the design of
a graph is important, the content is even more crucial to the delivery of
information. Graphs can have good design, but if the data or content is
flawed, the graph has no purpose. The data
on the X and Y axis of a
graph should always have some correlation, or some relationship that
can be demonstrated.
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