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Step 4: Displaying Information
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:
Different graphs are useful for different types of information, and it is important that the right graph for the type of data is selected.
- 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).
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.
A column graph usually represents discrete data. Note that a column graph has a gap between each column or set of columns.
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.
Figure 2: Example horizontal bar graph (Source: Australian Bureau of Statistics, ABS Publication 1331.0 Statistics: A Powerful Edge)
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.
Figure 3: Example histogram (Source: Australian Bureau of Statistics, (ABS Publication 1331.0 Statistics: A Powerful Edge))
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.
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 (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.
Figure 5: Example pie chart (Source: Australian Bureau of Statistics, (ABS Publication 1331.0 Statistics: A Powerful Edge))
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.
Figure 6: Example dot chart (Source: Australian System of National Accounts, 2005-06 cat. no. 5204.0)
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.
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
This page last updated 1 August 2011