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Evaluation Briefs
Using Graphs and Charts to Illustrate No. 12 | updated August 2018
Quantitative Data
Using visual representations to present data from Indicators for School Health, (SLIMS), surveys, or other evaluation
activities makes them easier to understand. Bar graphs, pie charts, line graphs, and histograms are an excellent way to
illustrate your program results. This brief includes concepts and definitions, types of graphs and charts, and guidelines
for formatting.
Major Concepts and Definitions Types of Graphs and Charts
Graphs and charts condense large amounts of ? A bar graph is composed of discrete bars that
information into easy-to-understand formats that represent different categories of data. The length or
clearly and effectively communicate important points. height of the bar is equal to the quantity within that
In selecting how best to present your data, think about category of data. Bar graphs are best used to
the purpose of your graph or chart and what you want compare values across categories.
to present, then decide which variables you want to
include and whether they should be expressed as
frequencies, percentages, or categories.
When you decide what kind of graph or chart best
illustrates your data, you should consider what type
of data you are working with. Categorical data are
grouped into non-overlapping categories (such as
grade, race, and yes or no responses). Bar graphs,
line graphs, and pie charts are useful for displaying
categorical data. Continuous data are measured on
a scale or continuum (such as weight or test scores).
Histograms are useful for displaying continuous data.
Bar graphs, line graphs, and histograms have an x- and
y-axis. The x-axis is the horizontal part of the graph and ? A pie chart is a circular chart used to compare parts
the y-axis is the vertical part. of the whole. It is divided into sectors that are equal in
size to the quantity represented.
C296013-H November 21, 2018
? A line graph displays the relationship between two Guidelines for Formatting Graphs and Charts
types of information, such as number of school
personnel trained by year. They are useful in ? Keep it simple and avoid flashy special effects. Present
illustrating trends over time. only essential information. Avoid using gratuitous options
in graphical software programs, such as three-dimensional
bars, that confuse the reader. If the graph or chart is too
complex, it will not clearly communicate the important
points.
? Title your graph or chart clearly to convey the purpose.
The title provides the reader with the overall message you
are conveying.
? Specify the units of measurement on the x- and
y-axis. Years, number of participants trained, and type
of school personnel are examples of labels for units of
measurement.
? Label each part of the chart or graph. You may need
a legend if there is too much information to label each
part of the chart or graph. (See the line graph). Use
? A histogram has connected bars that display the
different colors or variations in patterns to help the reader
frequency or proportion of cases that fall within
distinguish categories and understand your graph or
defined intervals or columns. The bars on the
chart.
histogram can be of varying width and typically display
continuous data. Resources
Minter E, Michaud M. Using Graphics to Report Evaluation
Results. University of Wisconsin Cooperative Extension.
2003.
Available at https://learningstore.uwex.edu/Using-Graphics-
to-Report-Evaluation-Results-P1022.aspx
Evaluation Briefs #12. Using Graphs and Charts to Illustrate
Quantitative Data.
Available at: https://www.cdc.gov/healthyyouth/evaluation/
pdf/brief12.pdf
For further information or assistance, contact the
Evaluation Research Team at ert@cdc.gov. You can
healthyyouth/evaluation/index.htm.

What type of graph is used to display categorical data? Bar graphs, line graphs, and pie charts are useful for displaying categorical data. Continuous data are measured on a scale or continuum (such as weight or test scores). Histograms are useful for displaying continuou.

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Title: Evaluation Briefs No 12
Subject: CS 296013-H
Author: CDC
Creator: Adobe InDesign CC 13.0 (Windows)