TECHNICAL NOTE 1 DATA QUALITY


RELIABILITY

1 Estimates in this release are based on information obtained from a sample survey (i.e. the Energy, Water and Environment Survey) conducted by the Australian Bureau of Statistics (ABS) for the 2011-12 reference year. Any collection of data may encounter factors that impact on 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 selecting a sample rather than conducting a census. This type of error is called sampling error.


Sampling error

2 Data for this publication was obtained using a sample of Australian businesses. Consequently, these data are subject to sampling variability, that is, they may differ from the figures that would have been produced if the data had been obtained from all businesses in the population. 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. 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 a census was conducted, and approximately 19 chances in 20 that the difference will be less than two standard errors.

3 Sampling variability can also be measured by 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 percentage errors likely to have occurred due to the effects of random sampling, and this avoids the need to refer also to the size of the estimate. Selected data item RSEs for Australia are shown in the table below. Detailed relative standard errors can be made available on request.

4 To illustrate, the estimated total of natural gas purchases for Transport, postal and warehousing in 2011-12 was $51m. The RSE of this estimate is shown as 3.1%, giving a standard error of approximately $1.6m. Therefore, there are two chances in three that, if all units had been included in the survey, a figure in the range of $49.4m to $52.6m 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 $47.8m to $54.2m.

5 When referring to Standard Errors of similar magnitudes, smaller estimates have higher RSEs. Percentage contributions when expressed as proportions are inherently smaller than one, therefore the size of the RSE may be a misleading indicator of the reliability of the estimates, particularly where the proportion is small.

Relative Standard Errors for key aggregates
	Quantity of electricity purchased	Quantity of natural gas purchased	Value of electricity purchased	Value of natural gas purchased
	%	%	%	%
Agriculture, forestry and fishing	11.4	65.2	9.4	85.6
Mining	1.4	0.3	1.4	0.6
Manufacturing	2.0	0.4	5.2	2.0
Electricity, gas, water and waste services	1.6	4.7	2.3	3.2
Construction	19.1	33.2	17.6	26.2
Wholesale trade	12.2	29.7	10.2	23.0
Retail trade	3.9	14.5	4.1	17.1
Accommodation and food services	13.6	14.4	7.7	13.5
Transport, postal and warehousing	4.8	1.3	7.7	3.1
Information, media and telecommunications	7.0	40.1	7.2	34.2
Financial and insurance services	27.1	96.9	17.1	55.7
Rental, hiring and real estate services	17.3	24.1	17.8	27.2
Professional, scientific and technical services	14.1	7.1	15.2	11.3
Administrative and support services	17.3	15.5	11.3	24.1
Public administration and safety	3.0	2.1	3.7	3.8
Education and training	2.1	3.3	1.6	3.1
Health care and social assistance	4.8	2.2	7.1	3.5
Arts and recreation services	8.4	6.0	8.6	5.5
Other services	8.7	23.5	10.9	17.9
Total selected industries	2.0	2.1	2.7	1.6

Non-sampling error

6 Errors other than those due to sampling may occur in any type of collection, whether a full census or a sample, and are referred to as non-sampling errors. All data presented in this publication are subject to non-sampling error. Non-sampling error 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 selected. The imprecision due to non-sampling variability cannot be quantified and should not be confused with sampling variability, which is measured by the standard error.

7 Although it is not possible to quantify non-sampling error, every effort is made to minimise it. 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.

8 Differences in accounting policy and practice across businesses 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 in the accounting policies and practices they adopt.

9 The above limitations are not meant to imply that analysis based on these data should be avoided, only that the limitations should be considered when interpreting the data. 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

10 In the 2011-12 Survey of Energy, Water and Environment, there was an 82.6% response rate from all businesses that were surveyed and found to be operating during the reference period. Data were imputed for the remaining 17.4% of operating businesses. This imputation contributed 7.4% to the total purchases of energy and fuels for all selected industries.


Data comparability

11 This section discusses the comparability of estimates with other ABS sources.


Comparison with other ABS statistics

12 The energy consumption figures presented in this publication may not be directly comparable with energy consumption statistics appearing in other publications. The main reason is due to differing scope and coverage (see Explanatory Notes for more detail). In addition the following points also lead to inconsistencies.

13 The consumption figures presented in this publication represent the cost and quantity of electricity and natural gas purchased by businesses. However, these figures do not reflect total energy consumed by the business, as described in the following.

14 These figures may exclude the value and quantity of energy produced and consumed in the intermediate steps of a businesses' production process. For example, when a business purchases black coal to produce coke, and then uses the coke to produce another product, the value and quantity of the intermediate fuel product (coke) is not reflected in the energy consumption figures for that particular business.

15 Energy end-use (final consumption) covers deliveries of commodities to consumers for activities that are not fuel conversion or transformation activities. Other publications may compile estimates on this basis, such as Energy Account, Australia, 2010-11 (cat. no. 4604.0). By contrast, the figures presented in this publication include commodities which are converted into other fuel types or products.

16 Amounts of electricity and natural gas purchased may not equal total amounts used. For example, the use of energy products sourced from a subsidiary business or from other businesses, where no corresponding financial transaction has taken place (non-monetary transaction).

17 The estimates for energy consumption do not include fuels, which were self-generated by the business.

18 Businesses that had a rent or lease agreement (lessees) did not report their electricity and natural gas expenditure and consumption. However, the lessor included the costs and usage of these fuels even though they were incurred by a separate business through a rent or lease arrangement.


Business counts

19 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 ABS information paper A Statistical View of Counts of Businesses in Australia (cat. no. 8162.0).

20 The Energy, Water and Environment Survey was not designed to provide high quality estimates of numbers of businesses which consumed and incurred expenses for various fuels surveyed. The number of businesses in the Energy use, electricity generation and environmental management, Australia, 2011-12 (cat. no. 4660.0) release are only included to provide contextual information for the user. (See Glossary for a more detailed explanation of number of businesses in the context of this publication).

21 A source of actual counts of Australian businesses is available from Counts of Australian Businesses, including Entries and Exits, Jun 2008 to Jun 2012 (cat. no. 8165.0), which was released in May 2013.