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QUALITY DECLARATION - SUMMARY
The WRTAL survey was designed to provide reliable estimates at the national level and for each state and territory. The number of completed interviews (after taking into account scope and coverage exclusions) was 19,976. The survey had a 72.1% response rate. The survey weighting ensured the responding population was representative of the estimated distribution of the population.
Two types of error are possible in an estimate based on a sample survey: non-sampling error and sampling error. Non-sampling error arises from inaccuracies in collecting, recording and processing the data. Every effort is made to minimise reporting error by the careful design of questionnaires, intensive training and supervision of interviewers, and efficient data processing procedures. Non-sampling error also arises because information cannot be obtained from all persons selected in the survey.
Sampling error occurs because a sample, rather than the entire population, is surveyed. One measure of the likely difference resulting from not including all dwellings in the survey is given by the standard error (SE). There are about two chances in three that a sample estimate will differ by less than one SE from the figure that would have been obtained if all dwellings had been included in the survey, and about 19 chances in 20 that the difference will be less than two SEs. Measures of the relative standard errors (RSE) of the estimates for this survey are included with this release.
Only estimates with RSEs less than 25% are considered sufficiently reliable for most purposes. Estimates with RSEs between 25% and 50% have been included and are annotated to indicate they are subject to high sample variability and should be used with caution. In addition, estimates with RSEs greater than 50% have also been included and annotated to indicate they are considered too unreliable for general use.
Another measure is the margin of error (MOE), which describes the distance from the population value of the estimate at a given confidence level, and is specified at a given level of confidence. Confidence levels typically used are 90%, 95% and 99%. For example, at the 95% confidence level the MOE indicates that there are about 19 chances in 20 that the estimate will differ by less than the specified MOE from the population value (the figure obtained if all dwellings had been enumerated). The MOEs in this publication are calculated at the 95% confidence level, and estimates of proportions with an MOE more than 10% are annotated to indicate they are subject to high sample variability. In addition, estimates with a corresponding standard 95% confidence interval that includes 0% or 100% are annotated to indicate they are usually considered unreliable for most purposes. For further information, please refer to the Technical Note.
The WRTAL survey was previously conducted in April 2013 as a supplement to the monthly LFS. The change of survey vehicle from a supplementary survey in 2013, to the MPHS in 2016-17 does not appear to have affected data comparability, as similar collection methodology was used, i.e. both were primarily personal telephone interviews, conducted after the LFS, with one randomly selected person from the household. The questions were the same for both surveys.
Comparison of WRTAL data and other ABS surveys such as the Survey of Education and Work (see Education and Work, Australia (6227.0)), and the Labour Force Survey should be undertaken with caution due to their different scope and sample sizes. Data from the WRTAL survey should be compared with caution to data collected in the Survey of Education and Training (see Education and Training Experience, 2009 (cat. no. 6278.0)) due to different collection methodologies used. For further information about data comparability, please refer to the Explanatory Notes.
To aid in the interpretation of the data, detailed information on concepts, definitions, terminology and other technical aspects of the survey can be found in the relevant web pages included with this release.
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