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TECHNICAL NOTE 2 DATA RELIABILITY
4 To illustrate the above, the estimate of total income for Transport, postal and warehousing in 2006-07 was $121,380m. The RSE of this estimate is shown as 2.1%, giving a standard error of approximately $2,549m (rounded). This implies that there are two chances in three that, if all units had been included in the survey, an estimate in the range of $118,831m to $123,929m would have been obtained. Similarly, it implies that there are 19 chances in 20 (i.e., a confidence interval of 95%) that the estimate would have been within the range of $116,282m to $126,478m.
5 The size of the RSE may be a misleading indicator of the reliability of some of the estimates for OPBT, EBITDA and IVA. This situation may occur where an estimate may legitimately include positive and negative values, reflecting the financial performance of individual businesses. In these cases, the aggregated estimate can be small relative to the contribution of individual businesses, resulting in a standard error which is large relative to the estimate.
6 All data presented in this publication are subject to non-sampling error.
7 The imprecision due to sampling variability, which is measured by the standard error, should not be confused with inaccuracies that may occur because of inadequacies in available sources from which the population frame was compiled, imperfections in reporting by providers, errors made in collection such as in recording and coding data, and errors made in processing data. Inaccuracies of this kind are referred to collectively as non-sampling error and they may occur in any enumeration, whether a full census or a sample.
8 Although it is not possible to quantify non-sampling error, every effort is made to reduce it to a minimum. Collection forms are designed to be easy to complete and assist businesses to report accurately. Efficient and effective operating procedures and systems are used to compile the statistics. The ABS compares data from different ABS (and non-ABS) sources relating to the one industry, to ensure consistency and coherence.
9 Differences in accounting policy and practices across businesses and industries can also lead to some inconsistencies in the data used to compile the estimates. Although much of the accounting process is subject to standards, there remains a great deal of flexibility available to individual businesses in the accounting policies and practices that they adopt.
10 The above limitations are not meant to imply that analysis based on these data should be avoided, only that the limitations should be borne in mind when interpreting the data presented in this publication. This publication presents a wide range of data that can be used to analyse business and industry performance. It is important that any analysis be based upon the range of data presented rather than focusing on one variable.
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