Graphs generated by the default settings of graphing software programs often require the user to perform time consuming or difficult visual tasks. Or, the graphs present visual messages that don't support the author's intended message. The most effective visual displays are created with an understanding of how the brain processes visual information and how people interpret visual patterns.

1. Optimizing the Visual Presentation
of Your Data
Mary Beth Hasselquist, MD
#stc15

2. Graphs constructed using principles
derived from knowledge of visual science
present
• the user with easy-to-perform visual
tasks and
• a visual message that’s congruent with
the intended message.
© 2015 Aktiva Design, Mary Beth Hasselquist

3. Designers encode data.
Users visually decode the data.
A graph is successful only if
the decoding process is effective.
Different types of graphs require
different tasks to decode the data.
© 2015 Aktiva Design, Mary Beth Hasselquist

4. Position along a common scale
Position along identical,
nonaligned scales Length
Angle
Slope
Area (and volume)
Color value
© 2015 Aktiva Design, Mary Beth Hasselquist
Decoding tasks from most accurate to least accurate

5. 605040302010
54.1
12.6
8.6
7.9
7.5
5.3
3.2
0.8
100%
Percent
A user is able to more accurately
decode data from a bar (or column)
graph than from a pie chart.
© 2015 Aktiva Design, Mary Beth Hasselquist

6. Column and bar graphs encode data in two ways:
• Length
• Position along a common scale
In order to encode the data accurately,
column and bar charts must start at zero.
© 2015 Aktiva Design, Mary Beth Hasselquist

7. Incorrect construction!
© 2015 Aktiva Design, Mary Beth Hasselquist

8. This column is 40%
as long as this column.
This column is 85%
as long as this column.
60
50
40
30
20
10
0
10 20 30 40
Predicted
probability of
adherence (%)
Copayment for 30-day supply of statin (USD)
Adherence to Statin Medication by Copayment
© 2015 Aktiva Design, Mary Beth Hasselquist

9. 60
50
40
30
20
10
0
10 20 30 40
Predicted
probability of
adherence (%)
Copayment for 30-day supply of statin (USD)
Adherence to Statin Medication by Copayment
44
46
48
50
52
54
56
58
60
10 20 30 40
Copayment for 30-day supply of statin (USD)
Adherence to Statin Medication by Copayment
Predicted
probability of
adherence (%)
If the intended purpose
of a graph is to highlight
the differences between
the variables and a column
(or bar) graph doesn’t meet
this intended purpose,
a point (dot) graph can be
used.
Point graphs encode data
using position along a
common scale.
© 2015 Aktiva Design, Mary Beth Hasselquist

10. 5.1%
16.0%
The addition of numerals at the top of columns
(or the ends of bars) adversely effects decoding
of the data.
Visually, the addition
of numerals lengthens
the columns.
The left column is about
two thirds as tall as the right.
The left column is about
one third as tall as the right.
Visually, these two columns
look more like this than this.
© 2015 Aktiva Design, Mary Beth Hasselquist

11. Gestalt principle of Proximity
Items that are closer together
will appear to belong together
as compared to items that are
further away.
Comp EPO HMO
POS PPO POS w/ca
CDHP HDHP Unknown
item 1
item 2
item 3
item 4
item 5
item 6
item 7
item 8
item 9
not
Comp EPO HMO
POS PPO POS w/ca
CDHP HDHP Unknow
item 1
item 4
item 7
item 2
item 5
item 8
item 3
item 6
item 9
© 2015 Aktiva Design, Mary Beth Hasselquist

12. Construct graphs so that the visual message
is congruent with the intended message.
A
10
0
5
15
Study population (%)
Treatment
No treatment
DCB
A
10
0
5
15
Study population (%)
No treatment
Treatment
DCB
Intended message: Treatment reduces risk compared to no treatment.
visually incongruent with
intended message
visually congruent with
intended message
© 2015 Aktiva Design, Mary Beth Hasselquist

13. Whenever possible, construct graphs
so that the math is done for the viewer.
A
10
0
5
15
Study population (%)
No treatment
Treatment
DCB
3.02.52.01.51.00.50
Absolute Risk Reduction of Treatment
B
A
C
D
Absolute risk reduction (%)
In this graph, users must
visually do the math to
determine the difference
between no treatment
and treatment for each
category.
In this graph, the math has been done for users.
© 2015 Aktiva Design, Mary Beth Hasselquist

14. Employing 3D effects, gradients and shadows
is almost always a poor design choice when
constructing graphs.
© 2015 Aktiva Design, Mary Beth Hasselquist

15. Design principles
• Use horizontal text within graphs
whenever possible for easier reading
• Order categorical data in a way that is
instructive, not arbitrary
• Use an appropriate scale
© 2015 Aktiva Design, Mary Beth Hasselquist

16. Hue
Saturation
Value
Color has three dimensions
© 2015 Aktiva Design, Mary Beth Hasselquist

17. Hue has no semantic meaning.
Any meaning associated with a
given hue is culturally determined.
© 2015 Aktiva Design, Mary Beth Hasselquist

18. Values have semantic meaning.
These meanings are universal.
Least
Most
© 2015 Aktiva Design, Mary Beth Hasselquist

19. Adobe Illustrator default Better
© 2015 Aktiva Design, Mary Beth Hasselquist

20. 3.02.52.01.51.00.50
Absolute Risk Reduction of Influenza-Related Complications 30-Days after Influenza Diagnosis
in Children with Chronic Medical Conditions Provided by Antiviral Treatment with Oseltamivir
Influenza-related
complication
Respiratory illness
other than pneumonia
Otitis media and
related complications
Pneumonia
Hospitalizations—
all-cause
Hospitalizations—
pneumonia-related
Hospitalizations—
non-pneumonia
respiratory illness
Absolute risk reduction (%)
3.02.52.01.51.00.50
Absolute Risk Reduction of Influenza-Related Complications 30-Days after Influenza Diagnosis
in Children with Chronic Medical Conditions Provided by Antiviral Treatment with Oseltamivir
Influenza-related
complication
Respiratory illness
other than pneumonia
Otitis media and
related complications
Pneumonia
Hospitalizations—
all-cause
Hospitalizations—
pneumonia-related
Hospitalizations—
non-pneumonia
respiratory illness
Absolute risk reduction (%)
Use color purposefully and only when it
contributes to the effectiveness of the graph.
A A
C
B
E
D
F F
E
D
C
B
In
this
graph,
color
has
no
intended
purpose
other
than
to
make
the
graph
“colorful.”
The
use
of
mul:ple
colors
degrades
the
pa;ern.
© 2015 Aktiva Design, Mary Beth Hasselquist

21. Any image created in color must work
in grayscale.
• Color documents are often reproduced
in grayscale.
• Certain visual information, such as information
about figure and ground, is carried to the brain
only in grayscale.
© 2015 Aktiva Design, Mary Beth Hasselquist

22. Because the values of some colors are similar,
when the chart is reproduced in grayscale, it is
difficult to distinguish the different wedges.
© 2015 Aktiva Design, Mary Beth Hasselquist

23. In order for us to easily read, there must
be sufficient contrast between figure
(text) and ground (background).
In order for us to easily read, there must
be sufficient contrast between figure
(text) and ground (background).
In order for us to easily read, there must
be sufficient contrast between figure
(text) and ground (background).
© 2015 Aktiva Design, Mary Beth Hasselquist

24. Mary Beth Hasselquist, MD
mb.hasselquist@gmail.com
206-660-9474
© 2015 Aktiva Design, Mary Beth Hasselquist