Information design
Key question
When is a graphic misleading?
Graphics appear objective, but can easily be misleading: through truncated axes, distorted areas, or cherry-picked timeframes. Sometimes this is deliberate, but often it's an oversight.
Learning objective: You can identify typical distortions, explain their effects, and present data honestly.
A graph can be misleading, even if all the figures are correct.
4.1 / Axes and Scale
The baseline defines the overall impression.
With bar charts, the eye compares the lengths of the bars. If the axis does not start at zero, small differences appear huge. Edward Tufte called the ratio of represented change to actual change the 'Lie Factor'; an honest value is close to 1.
For line charts, a non-zero axis can be useful when showing changes, provided it is clearly labelled.
Bars start at zero.
4.2 / Surfaces, 3D and Selection
Distortion takes many forms.
In addition to axes, there are other typical distortions:
01
Areas
If the height and width of a symbol are doubled, its area quadruples.
02
3D
Perspective distorts sizes; parts in the foreground appear larger.
03
Period
A well-chosen crop can invent a trend.
04
Cover
Absolute figures without reference to the size of the group are misleading.
In 'How Charts Lie', Alberto Cairo shows that even accurate charts can mislead if they conceal uncertainty or are presented without context.
Context is part of the truth.
4.3 / Sources and Uncertainty
Honesty is also reflected in the small print.
Every graphic needs a source, a date and, where necessary, an explanation of the methodology. This allows others to verify the statement.
Data often has uncertainties, such as in surveys or forecasts. Error bars, ranges, or a note make it visible how certain a statement is. Read more about honest design in Design Psychology, Section 8.2.
No source, no graphic.
Exercise
The same data, two stories
Task: Show how easily graphics can be misleading, and how to do it better.
STEP 1
Take a small data set with two to five values.
STEP 2
Create a deliberately exaggerated version: truncated axis, 3D, cherry-picked time frame.
STEP 3
Design an honest version with a zero baseline, source, and context.
STEP 4
Show both versions to others and ask for their impressions.
Evaluation: How much did the impressions differ?