3.1 Histograms with equal width bars
Histograms are often constructed using constant class intervals, in which case the height of each rectangle is proportional to the frequency of the variable (as in a bar chart).
(OED, 2025)
Above is the second part of the dictionary definition again. If the groups are of equal width, the height of the bars represents the frequency of each group.
Activity 7
Here is the village age demographic data again for the children’s play park investigation. This time it has been organised into groups of equal width.
Plot a histogram to represent this data.
Here is a reminder of a couple of points regarding good presentation from Week 4: Values on the axes should be evenly spaced and clearly labelled showing what information each axis represents, with units of measure if applicable. The chart should have a title describing what it shows. What advice would you give a learner before they start to draw the chart?
Answer
Here is an example of what your histogram may look like.
Key points to note for this histogram
The bars are equal width and there are no gaps between them The height of the bars represents the frequency of each group Frequency is a number so does not have a unit
You could ask a learner how many classes they will need for the horizontal axis. Some learners may start by writing 276 at the top of the vertical axis. You could advise them to plan an appropriate scale by finding the greatest and smallest values in the frequency column.