How to use statistics

What are statistics?

A statistic is information that has been produced by collecting, analysing, interpreting and communicating a sample of data. Statistics are important in helping us to understand what is happening in our society. They allow us to identify issues and opportunities, and provide us with the evidence to help us make decisions that will have a positive impact on our community.

Statistical terms and definitions

There are many terms that are used in statistics. Some of the most common ones are listed below.

  • Data – are measurements or observations that are collected as a source of information.
  • Frequency – the number of times a value appears in a dataset.
  • Mode – is the most commonly occurring number within a dataset.
  • Mean – is calculated by adding the value of each observation in a dataset and then dividing it by the total number of observations. It is also known as the ‘average’.
  • Median – is the middle value (or halfway point) of a dataset. For example, the City of Onkaparinga has a median age of 38 years. This means that half the people living in the city are over 38 years of age and half are under 38 years of age.
  • Population – refers to the number of people in a given area at a specific point in time. The term does not just refer to people but it can also refer to a collection of animals, plants or any other group that has at least one characteristic in common.

Different population measures

The population figures in our statistical products are mainly based on data from the Australian Bureau of Statistics (ABS) Census of Population and Housing (the Census). The aim of the Census is to accurately count the number of people in Australia on the night the Census is taken (Census night). It collects information on the characteristics of the population including age, gender, cultural background, education level and employment.

The Census occurs once every five years with the most recent Census being held on 9 August 2016.

There are different ways in which a population can be defined.   

  • The estimated resident population (ERP) is the ABS’s official estimate of Australia’s population and is based on Census data. The ERP provides a population figure between Censuses and is updated quarterly.
  • The place of usual residence population counts people based on where they usually live. The place of usual residence population is the most commonly used definition when interpreting Census data.
  • The place of enumeration population (enumerated population) counts people based on where they are located on Census night. This may or may not be the place where they usually live.
  • The working population includes all people that were employed in the week of the Census and provides information on where Australian workers are employed at the time of the Census. Place of work data only applies to those aged 15 years and over.

Different geographies

Similar to population figures, there are a number of ways in which geographical areas can be defined. These range from smaller areas such as suburbs, to larger regions such as states and territories. The most common way of defining the City of Onkaparinga is by local government area (LGA). When referring to information on the council area, this is the definition that is most often used in our statistics.

From July 2011, the ABS changed the way it defined geographical areas and replaced the previous Australian Standard Geographical Classification (ASGC) with the new Australian Statistical Geography Standard (ASGS). Under the ASGS, there are two broad categories as to how geographical areas are defined;  ABS structures and non-ABS structures. Detailed information related to ABS structures and statistical geography can be found on the ABS website.

In the City of Onkaparinga we have also defined a series of seven ‘districts’ across our region. Guided by the Community Plan as our lead strategic document we are using districts as a tool for the efficient planning and management of our activities.

The determination of these boundaries have considered demography, activity patterns and centres, urban form and land use and natural geographic boundaries. The districts each comprise whole suburbs, which enables the assessment of population and service data that is often available at the suburb level.

Recognising the diversity of our region at a district level will increase our local responsiveness through more localised demographic and spatial analysis to inform our service delivery. This assists us to consider local differences whilst being mindful of equity across our region.

The seven districts include:

  • Northern
  • Central North
  • Central South
  • Southern
  • Lonsdale
  • Hills North
  • Hills South

A map outlining these districts can be downloaded by clicking on the image below (3.4Mb).

Statistical districts