Basic Histogram Graphs

Histogram Chart
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In this lesson we will be looking at how to make a special type of statistics graph called a “Histogram”.

Drawing a Basic Histogram Video

The following three minute video shows the basics of drawing a simple Histogram.

 
 

How to Make Frequency Tables

We assume in this lesson that readers already know about survey type data, and how it can be placed into frequency tables.

The following is a Frequency Table which shows the number of coffees made per hour at a Cafe.

Note that 0-3 means zero to three cups of coffee were made in a one hour period.

The “Frequency” value of “2” for this item means that there were two separate hours where this situation occurred.

Frequency Table

If you do not have this background knowledge, then watch the following YouTube video.

Watch this video if you have not made a frequency table before.

 
 

Histogram Example

In this example, the Police were breath testing drivers for alcohol in a particular town. They did this for seven days, and the results are shown in the diagram below.

Drunk Survey Data

The first step we need to do for our Histogram graph is work out what units the scale along the vertical axis is going to be done in: ones, twos, fives, tens, etc.

There is a specific mathematical method for doing this.

Calculating Vertical Scale

The next step is to set up the horizontal axis, and the vertical axis for our graph.

Setting up the Axes

We can now Draw and Label each axis and add the Title at the top of our Histogram.

Draw and Label the Axes and Title

Our final step is to draw in each of the bars.

We need to make them all the same width, and start our graph with a half bar blank gap in the bottom left hand corner.

Each bar needs to go up as high as its second column Frequency value.

There must not be any blank gaps in between the bars. Eg. The bars must all touch each other along their vertical edges.

(Column Graphs and Bar Charts have gaps between bars, but Histograms do not).

In the graph shown below we have coloured in the bars different colours to give maximum impact.

Histogram with Colored Bars

Note that it is not necessary to colour in all of the bars different colours.

Usually Histogram bars are made all the one colour.

This helps to easily show the overall picture of the data.

Histogram with Yellow Bars

Histograms Summary

When creating a Basic Histogram from a Frequency Table, these are the steps that must be done:

Histograms Summary

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