Australian Bureau of Statistics
4402.0.55.001 - Microdata: Childhood Education and Care, Australia , June 2011
Latest ISSUE Released at 11:30 AM (CANBERRA TIME) 25/10/2012
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WEIGHTS AND ESTIMATION
As the survey was conducted on a sample of households in Australia, it is important to take account of the method of sample selection when deriving estimates. This is particularly important as a child's chance of selection in the survey varied depending on the state or territory in which they lived. Survey 'weights' are values which indicate how many population units are represented by the sample unit. See discussion in Survey Methodology.
There are two weights provided on the CEaCS CURF, as follows:
The application of weights ensures that:
Each record on the household level and person level also contains 60 replicate weights and, by using these weights, it is possible to calculate standard errors for weighted estimates produced from the microdata. This method is known as the 60 group Jack-knife variance estimator. When calculating standard errors, it is important to select the replicate weights which are most appropriate for the analysis being undertaken. The replicate weights are as follows:
Replicate weights enable variances of estimates to be calculated relatively simply. They also enable unit record analyses such as chi-square and logistic regression to be conducted which take into account the sample design. Replicate weights for any variable of interest can be calculated from the 60 replicate groups, giving 60 replicate estimates. The distribution of this set of replicate estimates, in conjunction with the full sample estimate (based on the general weight) is then used to approximate the variance of the full sample.
To obtain the standard error of a weighted estimate y, the same estimate is calculated using each of the 60 replicate weights. The variability between these replicate estimates (denoting y(g) for group number g) is used to measure the standard error of the original weighted estimate y using the formula:
g = the replicate group number
y(g) = the weighted estimate, having applied the weights for replicate group g
y = the weighted estimate from the sample.
The 60 group Jack-knife method can be applied not just to estimates of the population total, but also where the estimate y is a function of estimates of the population total, such as a proportion, difference or ratio. For more information on the 60 group Jack-knife method of SE estimation, see Research Paper: Weighting and Standard Error Estimation for ABS Household Surveys (Methodology Advisory Committee), July 1999 (cat. no. 1352.0.55.029).
Use of the 60 group Jack-knife method for complex estimates, such as regression parameters from a statistical model, is not straightforward and may not be appropriate. The method as described does not apply to investigations where survey weights are not used, such as in unweighted statistical modelling.
NOT APPLICABLE CATEGORIES AND SPECIAL CODES
For some data items, certain classification values have been reserved as special codes and must not be added as if they were quantitative values. These special codes generally relate to data items such as income, cost of care and number of hours of care. For example, code 99999998 for the data items 'Weekly income of mother' and 'Weekly income of father', refers to income 'Could not be determined'.
Furthermore, most data items included on the CURF include a 'Not applicable' category. The 'Not applicable' category, 99999997, for the data item 'Weekly income of mother' refers to no source of income or no mother in family. Similarly for 'Weekly income of father'. The 'Not applicable' category, 99999997, for the data item 'Weekly income of parent(s)' refers to no source of income. The classification value of the 'Not applicable' category and other special codes, where relevant, are shown in the data item list in the Downloads tab.
The population relevant to each data item is identified in the data item list and should be borne in mind when extracting and analysing data from the CURF. The actual population count for each data item is equal to the total cumulative frequency minus the 'Not applicable' category.
Generally all populations, including very specific populations, can be 'filtered' using other relevant data items. For example, if the population of interest is 'Children aged 0-12 who use formal care', any data item with that population (excluding the 'Not applicable' category) can be used.
For example, the CURF data items 'All reasons used formal care' (ARATTFC (A-L)) or 'Main reason used formal care ' (MRATFOCC) are applicable only to children aged 0-12 who use formal care. Therefore, either of the following filters could be used when restricting a table to 'Children aged 0-12 who use formal care' only:
ARATTFC < 99 or MRATFOCC > 0
(Note: For those data items, the 'Not applicable' categories (i.e. those children aged 0-12 who do not use formal care) are codes 99 and 0 respectively and would be excluded from either population filter shown above.)
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This page last updated 24 October 2012