1. Histogram – a picture of a Grouped Frequency Distribution
To accompany Hawkes lesson 2.2b (ii)
Original content by D.R.S.

2. Inputs and Outputs Output – a Histogram Numerical data
Input – Frequency Distribution
Output – a Histogram
Numerical data
Not categorical data
Grouped into classes
Each class has a count, a frequency, how many data values fall within that low-to-high class.
Horizontal axis has numerical class boundaries
Vertical axis has frequency of classes.
Height of each bar indicates the frequency of the each class
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3. Input: a frequency distribution
The data set: the 5K runners’ finishing times.
The data were grouped into a frequency distribution. Each class is a low-to-high range of temperatures.
We have the right ingredients for a histogram:
Frequency distribution (classes and counts)
Numerical data (not categorical)
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4. Recall – we had constructed this frequency distribution earlier.
Time (minutes)
Frequency 9 26 23 14 7 11 10 2 1

5. Recall this distinction between “Class Limits” vs. “Class Boundaries” – – –
Etc. – – –

6. Input: This frequency distribution of runners’ times
Time (minutes)
Frequency 9 26 23 14 7 11 10 2 1
For a histogram, we use the CLASS BOUNDARIES, not the class limits!

7. Histogram

8. Horizontal Axis
We used the Class Limits as our labeling on the horizontal axis.
This would probably make the most sense to the readers.
Time (in minutes)

9. Horizontal Axis But statistics books - and your assignments –
want the axis labels to be the class boundaries.

10. Important Design Notes!
The vertical axis begins at 0.
Tickmarks are well-chosen.
Axes – both horizontal and vertical axes – are labeled to tell the reader what the histogram is saying.
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11. TI-84 and Histogram STAT PLOTS has a histogram feature
But the screen size is so limited
TI-84 histograms might be useful for informal exploratory work
TI-84 histograms might be useful for small supplementary illustrations
But professional and business situations need something better
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12. Excel and Histograms
Being able to produce professional-looking charts in Excel is a very important today’s world !!!!!
It is well worth your time to develop your skills (and learn from your mistakes) NOW in this course, rather than waiting until you’re facing a deadline on a research paper or a workplace project.
See separate handouts for helpful info.
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13. Excel and Histograms
You can choose the “Column” chart and do it directly.
Or you can have the Data Analysis add-in generate the chart.
Either way, 90% of the job is quick & easy.
But it will take some thinking and some labor to turn the first graph into something professional.
Labels, titles, scaling, styling – these all take time
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14. Excel and Histograms Excel makes no distinction between
Histograms for numerical classes
Bar charts for categorical distributions
But this course makes a big deal about it
Some people “out there” make a big deal about it, too.
In many situations, your audience won’t know the difference.
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15. More resources Link to example with Excel, Insert, Column
Link to example with Excel, Data, Data Analysis, Histogram