TECHNICAL NOTE DATA QUALITY


RELIABILITY

1 The estimates in this release are based on information obtained from a sample survey, Retail and Wholesale Industries, Australia, 2012–13. Any collection of data may encounter factors that impact 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 The majority of data contained in this publication have been obtained from a sample of businesses. As such, 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 the data were obtained from only a sample of units. 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 units had been included in the collection, and about nineteen chances in twenty 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 key data items RSE at the Industry Division level for Australia are shown below. Detailed relative standard errors are available on request.


4 The size of the RSE may be a misleading indicator of the reliability of the estimates for (a) operating profit before tax, (b) earnings before interest, tax, depreciation and amortisation and (c) industry value added. It is possible for an estimate to legitimately include positive and negative values, reflecting the financial performance of individual businesses. In this case, 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.

RELATIVE STANDARD ERRORS BY INDUSTRY
		Total Retail Industry	Total Wholesale Industry
2012–13		%	%
Employment at end June
	Working proprietors and partners	5.3	17.1
	Employees	0.7	1.4
	Total	0.7	1.3
Income
	Sales of goods bought in and resold	0.7	1.4
	Income from services	4.3	5.2
	Other Income	5.3	6.6
	Total	0.7	1.5
Expenses
	Wages and salaries	0.8	0.9
	Other labour costs	0.9	1.0
	Purchases	0.8	1.5
	Payments to contractors and other businesses for freight, cartage, delivery and transport services	9.2	3.7
	Rent, leasing and hiring expenses
	Land, buildings and other structures	1.4	6.7
	Other rent, leasing and hiring	5.3	5.1
	Total	1.4	5.5
	Other Expenses	1.4	6.0
	Total	0.7	1.6
Inventories
	Opening	1.9	1.7
	Closing	1.9	3.6
	Operating Profit before tax	3.6	2.9
	Operating Profit Margin	3.5	3.2
	Industry Value Added	1.1	1.7

Non-sampling error

5 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. 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.

6 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, to ensure consistency and coherence.

7 Differences in accounting policy and practices across businesses and industries can also lead to some inconsistencies in the data provided 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.

8 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.
REFERENCE PERIOD

9 Where businesses were unable to supply data for the 12 months ended 30 June 2013, an accounting period for which data can be provided is used for data other than those relating to employment. All businesses were asked to report employment for the last pay period ending in June 2013.


QUALITY INDICATORS

10 In the 2012–13 Retail and Wholesale Industry Survey, there was an 80% response rate from all businesses that were surveyed and found to be operating during the reference period. Data were imputed for the remaining 20% of operating businesses. This imputation contributed 11% to the estimate of sales and service income for Retail and Wholesale industries.