A Brief Introduction to
Epidemiology - V
(Principles of Organizing &
Presenting Epidemiologic
Data)
Betty C. Jung, RN, MPH, CHES
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Learning Objectives
To
understand the proper methods
for organizing and presenting
epidemiologic data
To understand when tables, charts,
graphs and maps are appropriate
To understand the pitfalls of
improper data presentation
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Performance Objectives
Basic
understanding of the
importance in presenting
findings that are
understandable
Basic understanding of what
the right methods are for
presenting data
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Introduction
The primary purpose of organizing
and presenting data is to
communicate information about
the data.
Organizing data is essential to the
verification and analysis of data .
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Introduction
Data
are bits of observations that need
to be organized to provide information.
Data can be organized with:
– Tables
– Charts
– Graphs/Plots
– Maps
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Tables
Any
quantitative information can
be organized into tables
A table is a set of data arranged in
rows and columns
All percents should equal 100%
Should be self-explanatory
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Table Shell:General 2x2 Format
Exposed
Unexposed
Total
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Ill
a
c
v1
Well
b
d
v2
Total
H1
H2
T
Table Shell:Multi-variable Table
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Demographic
Number Percent
Characteristic
Age: <1 year
()
Age: 1 year+
()
Sex: Male
()
Sex: Female
()
Race: White
()
Race: Non-White
()
Total
(100%)
Charts
Charts
are methods used for
illustrating statistical
information using only one
coordinate.
Charts are most appropriate for
comparing data with discrete
categories.
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Chart Types
Bar
Group
Bar
Stack
Deviation
100%
Pie
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Component Bar
Chart Type:
Bar Chart
Used
to show the frequency
distribution of a variable with
discrete, noncontinuous
categories (i.e., sex, rate)
Can be either horizontal or
vertical
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Chart Type:
100% Component Bar Chart
Used
for comparing the
contribution of different
components to each of the
categories of the main
variable
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Chart Type:
Pie Chart
Useful
for showing the
component parts of a single
group or variable
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Graphs
Graphs
show quantitative data visually,
using a system of coordinates
Plots is another way to visually display
data
They serve as statistical snapshots that
help us see patterns, trends, aberrations,
similarities and differences in the data
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Graph Types
Arithmetic-scale
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Line Graphs
Semilogarithmic-scale Line
Graphs
Histograms
Frequency Polygons
Cumulative Frequency
Survival Curves
Graph Type:
Arithmetic-scale Line Graphs
Good
for actual changes on
the y-axis
Shows patterns or trends
over some variable (i.e., time)
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Graph Type:
Semilogarithmic-scale Line Graph
Good
for rates of change on
the y-axis
Equal distances on the y-axis
represent an equal percentage
of change
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Graph Type:
Histogram
Graph
of the frequency
distribution of a continuous
variable
Epidemic Curve - a
histogram of disease cases
during an outbreak or
epidemic
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Graph Type:
Frequency Polygons

Graph of a frequency
distribution (~ histogram)
 Good for showing and
comparing 2 or more
distributions on the same set
of axes
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Graph Type:
Cumulative Frequency
Plots
cumulative rather than
actual frequency for each
class interval of a variable
Good for identifying medians,
quartiles, and other
percentiles
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Graph Type:
Survival Curves
Used
with follow-up studies
to display the proportion of
one or more groups still alive
at different time periods
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Graph Type:
Scatter Diagrams (Scattergrams)
Used
for plotting the
relationship between 2
continuous variables
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Plots:
Dot Plots
Plots
one variable against
another
A visual comparison of the
actual data points of two
noncontinuous variables
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Plots:
Box Plots
Compare the distribution of
noncontinuous variables
“Box and Whiskers”
diagrams

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Maps
(Geographic Coordinate Charts)
Spot
Maps
Area Maps
Geographic Information
Systems
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Maps :
Spot Maps
Useful
for show the
geographic distribution of an
event
Does not take into
consideration the size of the
population at risk
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Maps:
Area Maps
Can
be used to show numbers
or rates
Showing rates can illustrate
differences in the risk of an
event occurring in different
areas
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Maps:
Geographic Information Systems
- “a computer system capable of
assembling, storing, manipulating, and
displaying geographically referenced
information.” (US Geological Survey)
GIS - “combines layers of information
about a place to give you a better
understanding of that place.” (GIS.com)
GIS
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Maps:
Geographic Information Systems
Improve
organizational
integration
Make better decisions
Make maps
(GIS.Com)
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References
For Internet Resources on the
topics covered in this lecture,
check out my Web site. Get
there from the shortcut.
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