TECHNICAL NOTE 1 DATA QUALITY


Quality indicators
Data comparability

RELIABILITY

1 The estimates in this release are based on information obtained from a sample survey (i.e. Health Care Services Survey) conducted by the Australian Bureau of Statistics (ABS). Any collection of data can be affected by factors that affect the reliability of the resulting statistics, regardless of the methodology used. These factors result in non-sampling error. In addition to non-sampling error, sample surveys are also subject to inaccuracies that arise from the fact that a sample was selected rather than conducting a census. This type of error is called sampling error.


Sampling error

2 Sampling variability occurs when a sample, rather than the entire population, is surveyed. It reflects the difference between estimates based on a sample and those that would have been obtained had a census been conducted. One measure of the likely difference is given by the standard error, which indicates the extent to which an estimate might have varied by chance because only a sample of units was included.

3 There are about two chances in three that a sample estimate will differ by less than one standard error from the figure that would have been obtained if all businesses/organisations had been included in the survey, and about 19 chances in 20 that the difference will be less than two standard errors.

4 Another measure of sampling variability is the relative standard error (RSE), which is obtained by expressing the standard error 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 sampling error in percentage terms, and this avoids the need to refer also to the size of the estimate. Selected data item RSEs at the aggregate level for Australia are shown in the table overleaf. Detailed relative standard errors can be made available on request.

Relative standard errors for Summary of operations, General practice medical services
					Australia
					%
Businesses at end June					1.3
Locations at end June					4.2
Persons working at end June
	Registered medical/health practitioners and other staff providing health care
		Employment
			Working proprietors and working partners of unincorporated businesses		5.2
			Employees
				Permanent full-time	5.3
				Permanent part-time	10.8
				Casual/temporary	23.4
				Total	6.5
			Total employment		4.7
		Persons working on contract			11.3
		Total			4.5
	Other staff				6.1
	Total persons working				4.3
Income
	Fee for service				4.3
	Government funding				14.9
	Other				10.1
	Total				3.5
Expenses
	Wages and salaries				2.8
	Other				6.0
	Total				4.1
Operating profit before tax					5.2
Operating profit margin					4.4
Industry value added					3.0

5 To illustrate the above, the estimate of total fee for service for general practice medical services in 2009-10 was $11,136m. The RSE of this estimate is shown as 4.3%, giving a standard error of approximately $479m. Therefore, there are two chances in three that, if all units had been included in the survey, an estimate in the range of $10,657m to $11,615m would have been obtained. Similarly, it implies that there are nineteen chances in twenty (i.e. a confidence interval of 95%) that the estimate would have been within the range of $10,178m to $12,094m. The size of the RSE may be a misleading indicator of the reliability of some of the estimates for (a) operating profit before tax and (b) industry value added. It is possible for an estimate legitimately to include positive and negative values, reflecting the financial performance of individual businesses/organisations. In this case, the aggregated estimate can be small relative to the contribution of individual businesses/organisations, resulting in a standard error which is large relative to the estimate.

Non-sampling error

6 Error other than that due to sampling may occur in any type of collection, whether a full census or a sample, and is referred to as non-sampling error. It can arise from 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. It also occurs when information cannot be obtained from all businesses/organisations selected.

7 Businesses/organisations contributing to the estimates in this publication were sourced from the ABS Business Register (ABSBR). A known source of non-sampling error exists in the ABSBR relating to the misclassification of units in accordance with the Australian and New Zealand Standard Industrial Classification (ANZSIC) 2006 edition (cat. no. 1292.0). In many cases businesses/organisations can be classified correctly at the division and sub division level of ANZSIC06, yet at the class level are misclassifed, with the greatest impact on ANZSIC 8511 General practice medical services.

8 Although it is not possible to quantify non-sampling error, every effort was made to reduce it to a minimum. Collection forms were designed to be easy to complete and assist businesses/organisations to report accurately. Efficient and effective operating procedures and systems were used to compile the statistics. The ABS compared 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/organisations and industries can 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/organisations 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.

QUALITY INDICATORS

11 In the 2009-10 survey of health care services, there was a 92.6% response rate from all businesses/organisations that were surveyed and found to be operating during the reference period. Data were imputed for the remaining 7.4% of operating businesses/organisations. Imputed responses contributed 6.4% to the estimate of total income for all selected industries.


DATA COMPARABILITY

Comparison with other ABS statistics

Australian Industry (cat no. 8155.0)

12 Key annual industry data for ANZSIC06 subdivisions 85 Medical and other health care services are published in Australian Industry (cat. no. 8155.0). There are important differences between statistics published in Australian Industry and Health Care Services and users should exercise caution when making comparisons between the two sets of estimates. A key difference is the inclusion of micro non-employers in Australian Industry.

13 Australian Industry presents annual summary statistics at the ANZSIC06 division and subdivision levels. It shows the relative performance of each industry division and subdivision, and allows patterns of change of growth to be analysed across particular segments of the Australian economy.

14 Health Care Services supplements Australian Industry statistics with a detailed examination of the structure and performance of health care services businesses/organisations for the reference year of the survey. As such, the survey is not designed to monitor change over time.

Counts of Australian Businesses, including Entries and Exits (cat. no. 8165.0)

15 Estimates of the number of businesses operating in Australia can be derived from a number of sources within the ABS. They may relate to a particular point in time or may be presented as an average annual figure. However, these estimates will not always show the same results. Variations will occur because of differing data sources, differing scope and coverage definitions between surveys, as well as variations due to sampling and non-sampling error. More information about business counts can be found in the information paper A Statistical View of Counts of Businesses in Australia (cat. no. 8162.0).
16 The Health Care Services Survey is not designed to provide high quality estimates of numbers of businesses/organisations for any of the output classifications (for example, business size or industry) and the number of businesses/organisations in this publication are only included to provide contextual information for the user. A more robust source of counts of Australian businesses is available from Counts of Australian Businesses, including Entries and Exits, Jun 2007 to Jun 2009 (cat. no. 8165.0).

Historical comparisons

17 The reader should bear in mind that this survey was not designed to support accurate estimates of change over time. There have been major changes to the statistical units, frame, scope, industry classification and estimation methodology between the 2001-02 Private Medical Practitioners and Private Medical Practices; the 1997-98 suite of Selected Allied Health Services (Dental Services, Optometry and Optical Dispensing Services, Physiotherapy Services, Chiropractic and Osteopathic Services, Audiology and Audiometry Services), and the 2009-10 Health Care Services Survey. These include:

• use of the ABSBR frame instead of external frames. In previous survey iterations a two phase approach was used. Medical practitioners were identified from listings provided by Medicare and from allied health practitioner listings provided by industry associations. These practitioners were then asked to provide details of the practice or business they worked for. In the second phase of the survey, data was collected from the practice or business identified in the first phase of the survey.
• changes to the statistical unit as a result of the introduction of The New Tax System on 1 July 2000
• changes to scope as a result of including significant non-employing units in the survey
• major changes between the 1993 and 2006 editions of ANZSIC which affected some health care services sectors
• the use of generalised regression estimation methodology instead of number raised estimation.
• the introduction of the new Australian Equivalents to International Financial Standards (AEIFRS) from 1 January 2005, resulting in changed definitions applying to some items in the financial accounts of Australian businesses.

18 Consequently, estimates in this issue are not directly comparable with those in the 2002 Private Medical Practitioners and 2001-02 Private Medical Practices publications, and the 1997-98 Selected Allied Health suite of publications and users are advised against making historical comparisons.