A Brief Introduction to Epidemiology - V (Principles of Organizing

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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 ShellGeneral 2x2 Format
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Table ShellMulti-variable Table
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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 Component Bar
• Pie

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Chart TypeBar 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 Type100 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 TypePie 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 Line Graphs
• Semilogarithmic-scale Line Graphs
• Histograms
• Frequency Polygons
• Cumulative Frequency
• Survival Curves
• Scatter Diagrams (Scattergrams)

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Graph TypeArithmetic-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 TypeSemilogarithmic-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 TypeHistogram

• 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 TypeFrequency 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 TypeCumulative 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 TypeSurvival 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 TypeScatter Diagrams (Scattergrams)

• Used for plotting the relationship between 2
  continuous variables

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PlotsDot Plots

• Plots one variable against another
• A visual comparison of the actual data points of
  two noncontinuous variables

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PlotsBox 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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MapsGeographic Information Systems

• GIS - 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)

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MapsGeographic 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.