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SUMMARY OF FINDINGS
1 This publication presents results, in respect of 1998–99, from an Australian Bureau of Statistics (ABS) survey of 852 businesses mainly engaged in providing security and investigative services.
2 The scope of the survey was all employing businesses recorded on the ABS business register and classified to Class 7864, Security and Investigative Services, of the Australian and New Zealand Standard Industrial Classification (ANZSIC). Class 7864 includes businesses mainly engaged in providing protection or private enquiry services, other than police forces and government security agencies. Businesses mainly providing locksmith services, alarm wholesaling and security equipment installation services were not included in the survey.
IMPROVEMENTS TO COVERAGE
3 Data in this publication have been adjusted to allow for lags in processing new businesses to the ABS business register, and the omission of some businesses from the business register. The majority of businesses affected and to which the adjustments apply are small in size.
4 Adjustments have been made to include new businesses in the estimates in the periods in which they commenced operations, rather than when they were processed to the business register. Adjustments of this type will continue to be applied in future periods.
5 Further adjustments have been made for businesses which had been in existence for several years, but, for various reasons, were not previously added to the ABS register. The ABS is remedying these omissions.
6 For more information on these adjustments, please refer to the ABS publication 'Information Paper: Improvements to ABS Economic Statistics, 1997' (Cat. no. 1357.0).
7 The unit for which statistics were reported in the survey was the management unit. The management unit is the highest-level accounting unit within a business or organisation, having regard to the required level of industry homogeneity, for which a set of accounts is maintained. In most cases it coincides with the legal entity owning the business (i.e. company, partnership, trust, etc.). However, in the case of large diversified businesses, there may be more than one management unit, with each coinciding with a 'division' or 'line of business'. A division or line of business is recognised where separate and comprehensive accounts are compiled for it.
8 Data contained in the tables in this publication relate to all security and investigative services businesses which operated in Australia at any time during the year ended 30 June 1999. Counts of businesses include only those businesses that were operating at 30 June 1999.
RELIABILITY OF THE DATA
9 The estimates in this publication are subject to sampling and non-sampling error.
10 The estimates in this publication are based on information obtained from a sample of businesses in the surveyed population. Consequently, the estimates in this publication are subject to sampling variability, that is, they may differ from the figures that would have been obtained if all units had been included in the survey. One measure of the likely difference is given by the standard error (SE), which indicates the extent to which an estimate might have varied by chance because only a sample of units was included.
11 There are about 2 chances in 3 that a sample estimate will differ by less than one SE from the figure that would have been obtained if a census had been conducted, and approximately 19 chances in 20 that the difference will be less than two SEs.
12 Sampling variability can be measured by the relative standard error (RSE) which is obtained by expressing the SE as a percentage of the estimate to which it refers. The RSE is a useful measure in that it provides an immediate indication of the percentage errors likely to have occurred due to sampling, and this avoids the need to refer also to the size of the estimate.
13 The following table contains estimates of RSEs for a selection of the statistics presented in this publication.
14 As an example of the above, an estimate of total income for the security services industry is $1,394.8 million and the RSE is 2%, giving a SE of $27.9 million. Therefore, there would be 2 chances in 3 that, if all units had been included in the survey, a figure in the range of $1,366.9 million to $1,422.7 million would have been obtained, and 19 chances in 20 (i.e. a confidence interval of 95%) that the figure would have been within the range of $1,339.0 million to $1,450.6 million.
15 Errors other than those due to sampling may occur because of deficiencies in the register of units from which the sample was selected, non-response, and imperfections in reporting by respondents. Inaccuracies of this kind are referred to as non-sampling errors and they may occur in any collection, whether it be a census or a sample. Every effort has been made to reduce non-sampling error to a minimum by careful design and testing of questionnaires, efficient operating procedures and systems, and appropriate methodology.
16 ABS publications draw extensively on information provided freely by individuals, businesses, governments and other organisations. Their continued cooperation is very much appreciated; without it, the wide range of statistics published by the ABS would not be available. Information received by the ABS is treated in strict confidence as required by the Census and Statistics Act 1905.
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