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In this issue, we will focus on understanding statistical concepts. There are three basic forms of statistical representation: tables, graphs and maps.
The ABS presents much of its information in the form of tables where data is presented in rows and columns. By following some simple principles, information can be quickly understood from a table.
Once you are clear on what the table is about, proceed to the actual figures and extract the information you require. Over time, you will be able to interpret tables more quickly and accurately. It is good practice, however, to be methodical and follow the steps above any time you use a table.
Why is there variation in the data?
Figures will often vary slightly from table to table due to randomisation. Introduced random error is a technique that was developed to avoid identification of individuals. Prior to the 2006 Census, the confidentiality technique applied by the ABS was to randomly adjust cells with very small values. For the 2006 Census, a new technique was developed which slightly adjusts all cells to prevent identifiable data being exposed. These adjustments result in small introduced random errors, but do not impair the value of the table as a whole.
Tables which have been randomly adjusted will be internally consistent, however comparisons with other tables containing similar data may show minor discrepancies. This is the case for both customised tables and standard products. These small variations can, for the most part, be ignored.
Information that is presented visually is often easier to understand. Graphs are an ideal way to show trends or differences between data. It is important to interpret scales accurately to avoid misinterpretation of the data. The ABS uses various types of graphs to illustrate different types of data:
UNEMPLOYMENT RATE, Tasmania
NEW RESIDENTIAL BUILDING APPROVALS, top 10 contributors to the state total,
by local government area, Tasmania, 2007-08
TYPE OF INTERNET CONNECTION, Tasmanian dwellings(a),
by statistical division, August 2006
POPULATION CHANGE, Tasmania, 1996-2006
Source: Census of Population and Housing, 1996, 2006
ABS data available on request
Maps provide a simple visual comparison between geographic areas. Legends must be interpreted accurately to fully understand information presented in this way. The map below is based on the 2006 Census. It shows the unemployment rate by local government area, identifying areas with the highest rate of unemployment in red, grading to areas with the lowest rate in yellow. In 2006, the highest rate of unemployment (10.3%) was in the George Town Local Government Area (LGA), followed by Kentish (9.6%) and Break O'Day (9.2%). The lowest rates of unemployment were in King Island (2.2%), Flinders (3.8%) and Circular Head (4.2%) respectively.
Insets can draw out finer detail, such as rates of unemployment around the Hobart area, where the highest rate of unemployment was found in the Derwent Valley (9.0%) and the lowest was in Kingborough (4.5%).
UNEMPLOYMENT RATE, by local government area, August 2006
Source: Census of Population and Housing, 2006
ABS data available on request
For further explanation of terms see Statistical Language! (ABS cat. no. 1332.0.55.002)
In upcoming issues of Tasmanian Statistical News we will discuss other statistical literacy concepts in more detail. Meanwhile, if you would like to know more about statistical literacy and its relevance to you, check out the article: What is statistical literacy and why is it important to be statistically literate? as featured in Tasmanian State and Regional Indicators (ABS cat. no. 1307.6) or visit the Understanding Statistics portal on the ABS website.
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