A histogram enables us to graphically represent the distribution of data.

Creating Histograms

To create a histogram, we need a table like the one on the rights. You have to know the classes (height (m)) and the frequency. Then you need to calculate the frequency density. The formula for this is: In this example, the first calculation is 33 divided by 3. As a result, the frequency distribution is 11. After you have done this for all classes, you can start plotting the graph. It is like a bar chart just that the bars can have a different thickness. The frequency distribution always goes into the y-axis so you can easily determine how high the bar will be (since the frequency distribution of the first class is 11, the bar goes until 11 on the graph). The x-axis is the class width and is labelled with the measurement of the class. In this case heigh (m). You have already found the class width before when finding the frequency distribution. Now you should be able to plot all the bars. As an example, we found that the frequency distribution of the first class is 11 and that the class width is 3. As a result, the first bar is 11 high and 3 wide.
Height (m) Frequency Distribution Frequency Class Width

Decimals in Data Histograms

To make it easier to understand, we have ensured that all the values in the example above are whole numbers. However, this will not always be the case. The frequency distribution or even the class width may be a decimal number. In this case, it just becomes a bit harder to calculate. The method is the same.

Box and Whiskers

We recommend that you try to do some box and whiskers next. Box and whiskers allow you to graphically represent the spread of data by showing the quartiles. Please share this page if you like it or found it helpful!
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Chapter 22.6:  Learning Outcomes Students will learn how to calculate the frequency density! Students will learn how to create histograms! Students will learn how to interpret histograms!



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