Histograms in Geography
What is a histogram?
A histogram appears similar to a bar chart. However, there are key differences between the two. Histograms are used to present continuous data (a bar chart is used to present discrete data).
When is using a histogram appropriate?
Histograms are ideal for presenting continuous data. Continuous data is data that falls in a continuous sequence e.g. time, distance and temperature. An example of this would be after counting pedestrians at 15 minute intervals over 2 hours, a histogram could be used to present the results.
Creating a histogram
Creating a histogram is relatively simple. In this example we are going to produce a histogram to show the results of a pedestriam count completed at 15 minute intervals over a continuous period of time. Students have collected raw data that shows the number of pedestrians that passed them during 15 minute intervals over two hours.
- 8-8.15 am – 120
- 8.15-8.30 am – 156
- 8.30-8.45 am – 176
- 8.45-9 am – 167
- 9-9.15 am – 101
- 9.15-9.30 am – 134
- 9.30-9.45 am – 123
- 9.45-10 am – 132
Step 1 – Decide on the scale of the X-axis
Decide on an appropriate scale on the X-axis for the bars. The bars should be the same width and there should be no gaps between the bars.
Step 2 – Decide on the scale of the Y-axis
Decide on a suitable scale for the Y-axis for the number of pedestrials. The scale should be spaced evenly and allow for the highest number in the data set to be included.
Step 3 – Create the histogram
Accurately draw the bars for each piece of data. As the data is continuous, each bar should be shaded in a the same colour
Step 4 – Finish your graph
Include a title and label each axis.
Reading a histogram
To read a bar chart, read along the x-axis (bottom) to find the bar you want to read. Go to the top of the bar and read across to the scale on the y-axis to work out the value. Using a a ruler can help with this.
Create your own histogram