1.Composite bar charts
If something is made up of multiple parts or elements, we might refer to it as ‘composite’. So, if the data we are given can be broken down into multiple sections or if we have multiple datasets to collate into one graph we might use a composite representation.
Image to represent composition such as thisThe bars in the composite bar chart shown in Figure 1are drawn as stacked sections to communicate information about total frequencies and individual components. The total height of the bar tells you the total frequency. The height of each part of the bar tells you how many are in a category. This is also sometimes called a compound bar chart or stacked bar chart.
In Figure 1 it is quick to see that the most common origin of guests at the hotel is Ireland, but you can also find out that the most adults came from Britain, or that no children came from mainland Europe.
Figure 1 Composite bar chart showing origin and age distribution of guests at a hotel Composite bar chart taken from ‘Succeed with Maths Part 2’ BOC Week 8 Figure 16.Activity 1
Graphical representations of data are often used in the media such as this composite bar chart showing UK government spending data (in billions of pounds, £bn) provided by the Office for Budget Responsibility (OBR).
Figure 2 Composite bar chart showing distribution of government spending by department Source: https://news.sky.com/story/the-five-things-you-need-to-know-about-the-spending-review-13381750 (Note RDEL stands for Resource Departmental Expenditure Limits, read the article for an explanation of what this means.) from Ana : Maybe the note should be in a footnote?In her spending review the Chancellor of the Exchequer made these statements:
“In this spending review, total departmental budgets will grow by 2.3% a year in real terms.”
“Overall, I am providing a cash uplift of over £4.5 billion a year in additional funding for the core schools budget by the end of the spending review, backing our teachers and our kids. …I am therefore providing investment, rising to nearly £2.3 billion per year, to fix our crumbling classrooms, in addition to £2.4 billion per year to continue our programme to rebuild 500 schools…” (Reeves, 2025)
Think about whether the graph in Figure 2 reflects these statements; note down what can be seen from the graph and what cannot.
Comment
There are many possible reflections that could be made here, these are just a couple of points.
From the increase in overall bar height, the graph seems to be indicating a growth in total day to day spending, however, it is not possible to clearly estimate the percentage of that growth from the scales given; using a grid instead of plain background would aid interpretation.
The ‘education’ section of each bar can be seen for the three date periods shown and it appears this may be slightly bigger for 2025-26 compared to previous years however, again, it is difficult to make direct statements about values without a grid. Also, the statement talks about the ‘core schools budget’ and it is not known whether this is referring to the whole of the education section or just part of it i.e. that the education budget could further be broken down into more defined areas.
Whilst a composite bar chart can be a nice way to visually communicate a lot of information in one graph, in doing so, much of the fine detail is lost.