2. Histograms are a great way to graphically represent
a specific type of data known as “frequency data.”
A histogram of frequency data is constructed by
first identifying a number of equal “intervals” that
will become your bins (e.g. 0-1, 1-2, 2-3; or 0-2, 2-
4, 4-6, and so on).
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3. The challenge is selecting the correct set of equal
intervals that sufficiently reduces the information
into a readable form but also provides enough
variability to enable viewers to see the shape of the
distribution (i.e. the story of the data). We’ll
explore appropriate bin sizes in Module 3.
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4. “Frequency data” is the hallmark of histograms. This
is the type of data occurs when a specific event
happens within an interval. For
example, standardized test scores represented in
“percentiles” (e.g. 90th percentile) are frequency
data.
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5. BAR CHARTS are often used for quantitative or
categorical data, not frequency distribution. The
chart below is measuring categorical data.
Unfortunately, bar charts can also be used for
frequency distributions so long as the number of
unique scores in the data set is not large.
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6. In business, since both histograms and bar charts can be
effectively used to represent the same data set, there can be
a lot of confusion over which chart to use or even which one
you’re looking at! For example, what kind of chart is the one
below, a histogram or a bar chart? It’s not as easy as it
seems. The following slides will demonstrate the similarities
and differences between histograms and bar charts.
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7. SAMPLE HISTOGRAM
Numerical Element Continuous Range
Frequency (Number of Batches)
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0-5 6-10 11-15 16-20 21-25 26-30 31-35 36-40

8. SAMPLE BAR CHART
Discrete Element Non-Continuous Item
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9. HEAD TO HEAD
Histogram Bar Chart
Method of presenting comparisons Visual representation of comparing values
Grouped or continuous items Non-grouped, non-continuous items
Usually numbers presented in ranges Visual comparison of discrete elements
Bars need to be touching in display Bars don’t need to be touching in display
(thanks Microsoft for not doing this!)

10. CRITICAL THINKING: Can you think of a situation
that you’ve experienced where a histogram
would provide more useful information than a
bar chart (think large data set and frequency
distribution)?
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