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Step 4: Displaying Information
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Bar GraphsPie Charts
HistogramsDot Charts
Line GraphsAge Pyramids


One of the most powerful ways to communicate data is by using graphs. Data which is presented in a graph can be quick and easy to understand.
A graph should:
  • be simple and not too cluttered
  • show data without changing the data’s message
  • clearly show any trend or differences in the data
  • be accurate in a visual sense (e.g if one value is 15 and another 30, then 30 should appear to be twice the size of 15).
Different graphs are useful for different types of information, and it is important that the right graph for the type of data is selected.


Bar Graphs

A bar graph may be either horizontal or vertical. To differentiate between the two, a vertical bar graph is called a column graph. An important point about bar graphs is the length of the bars: the greater the length, the greater the value.


Column Graph

A column graph usually represents discrete data. Note that a column graph has a gap between each column or set of columns.

Image: Example of a bar graph.
Figure 1: Example column graph (Source: Australian Bureau of Statistics, (2001 Census of Population and Housing))

The above graph is a multiple column graph. It makes comparisons between males and females easier to understand.

It is important that each graph has a heading, the axes are labelled and there is a key. Notice that each axis is evenly divided.

Horizontal Bar Graph

The advantage of a horizontal bar graph over a column graph is that the category labels in a horizontal bar graph can be fully displayed making the graph easier to read.

Graph: Employed persons by occupation and sex, Australia, 1996 Census
Figure 2: Example horizontal bar graph (Source: Australian Bureau of Statistics, ABS Publication 1331.0 Statistics: A Powerful Edge)


Histograms

A histogram is similar to a column graph, however, there is no gap between columns. The frequency is measured by the area of the column. Generally, a histogram will have equal width columns, although when class intervals vary in size this will not be the case. Choosing the appropriate width of the columns for a histogram is very important.

Image: Example of a histogram
Figure 3: Example histogram (Source: Australian Bureau of Statistics, (ABS Publication 1331.0 Statistics: A Powerful Edge))

Line Graphs

Line graphs should always be used when you are trying to display a trend in data over time. When drawing line graphs, it is important to use a consistent scale on each axis, otherwise the line's shape can give incorrect impressions about the information.

Image: Example of a line graph
Figure 4: Example line graph (Source: Australian Demographic Statistics, cat. no. 3101.0; Australian Demographic Trends, cat. no. 3102.0; (Official Year Book of the Commonwealth of Australia, 1901-1910))

Pie Charts

Pie charts (often called pie graphs, sector graphs or sector charts) are used for simple comparisons of a small number of categories that make up the total number of responses. Using more than five categories will make a pie chart difficult to read.

It is very important to label the slices with their actual values to make the comparison easier.

Image: Example of a pie chart
Figure 5: Example pie chart (Source: Australian Bureau of Statistics, (ABS Publication 1331.0 Statistics: A Powerful Edge))

Dot Charts

A dot chart is able to convey a lot of information in a simple way without clutter. It contrasts values very clearly, and can display many data values.


Image: example of a dot chart.
Figure 6: Example dot chart (Source: Australian System of National Accounts, 2005-06 cat. no. 5204.0)

Age Pyramids

To represent the population age structure, the ABS uses an age pyramid. Age pyramids are a very effective way of showing change in a country’s age structure over time, or for comparing different countries. Estimates and projections of Australia's population from 1971 to 2050 are available on the ABS Animated Age Pyramid page.


Image: example of a age pyramid.
Figure 7: Example age pyramid (Source: Australian Bureau of Statistics)

In this section:

Step 1: A Problem to Solve
Step 2: Collecting Data
Step 3: Organising Data
Step 4: Displaying Information
Step 5: Drawing Conclusions

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