Quality Declaration
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CONFIDENTIALITY In accordance with the Census and Statistics Act 1905, all estimates are subjected to a confidentiality process before release. This confidentiality process is undertaken to avoid releasing information that may allow the identification of particular individuals, families, households, dwellings or businesses. Processes used in TableBuilder to confidentialise records include the following:
To minimise the risk of identifying individuals in aggregate statistics, a technique is used to randomly adjust cell values. This technique is called perturbation. Perturbation involves small random adjustments of the statistics and is considered the most satisfactory technique for avoiding the release of identifiable statistics while maximising the range of information that can be released. These adjustments have a negligible impact on the underlying pattern of the statistics. The introduction of these random adjustments will result in tables not adding up. Randomly adjusted individual cells will be consistent across tables, but the totals in any table will not be the sum of the individual cell values. The size of the difference between summed cells and the relevant total will generally be very small, as demonstrated below. The introduction of perturbation in publications ensures that estimates produced in TableBuilder are consistent with published statistics. The estimates of error produced using TableBuilder may show small differences relative to published estimates of error. These differences are not statistically significant. Table suppression Some tables generated within TableBuilder may contain a substantial proportion of very low counts within cells (excluding cells that have counts of zero). When this occurs, all values within the table are suppressed in order to preserve confidentiality. The following error message displayed at the bottom of the table indicates when table suppression has occurred. ERROR: The table has been suppressed as it is too sparse.
If field exclusion rules exist for certain variables, users will see the following message: Maximum number of fields in exclusion group exceeded EXAMPLE: USING MULTIPLE RESPONSE DATA ITEMS A number of data items produced from the SDAC allow a respondent to provide more than one response. These are referred to as multiple response data items. An example of one of these items being used within the TableBuilder is shown below. In this example, a series of questions are asked in the survey, relating to each activity, in order to produce the data item 'Type(s) of activity for which aid(s) or equipment used'. Responses to these questions determine whether an aid or equipment is used for a given activity. A person may indicate the use of an aid or equipment for more than one activity, meaning they have supplied multiple responses to this data item. When a multiple response data item is tabulated, a person is counted against each category, for which they have provided a response (e.g. a person who uses an aid(s) or equipment for Toileting, Dressing and Eating will be counted against each of these three categories). Similar to a single response data item, a person not within the appropriate population will fall into the ‘Not Applicable’ category (e.g. a person without a disability is not asked about their use of an aid or equipment and is therefore considered ‘Not Applicable’ for this data item). A category exists for persons who are in scope of the population, but do not provide a valid response to any other categories (i.e. a person requiring assistance for one or more activities, but who does not use an aid or equipment for any activities will fall into the category ‘Does not use aids or equipment’). Therefore, each person in the appropriate population is counted at least once, while some persons are counted multiple times. The total for multiple response data items is therefore less than or equal to the sum of its components. In the example below, the sum of the components is 25,418.9. The table below draws upon ‘Whether has a disability’ from the Person level and ‘Extent to which need for assistance is met’ from the Broad Activities level. This table is followed by a practical demonstration of how estimates may be derived when using sub-person levels. Note: In order for a person to contribute record(s) to the Broad Activities level they must experience difficulty with one or more broad activities. A record is created for each activity where the person experiences difficulty. In the table above, the sum of the components is far greater than the total (6,342 versus 4,234.2). This is because, for each activity where a person experiences difficulty, a response is required to the item ‘Extent to which need for assistance is met’. A person can experience difficulty in multiple activities and can therefore contribute more than one record to the response categories for this item (i.e. Fully, Partly, Not at all and Not applicable). The ‘Total’ refers to the number of persons contributing to the table and is derived from the person level item ‘Whether has a disability’. Only one record can be attributed to a Person level item, unless the response categories for that item allow multiple responses. An example of how this table is derived is shown below, where the population consists of just one person:
Note re Table c:
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