Sampling Procedure
Sampling Design
The South African Social Attitudes Survey has been designed to yield a representative sample of adults aged 16 and older. The sampling frame for the survey is the Human Sciences Research Council’s (HSRC) Master Sample, which was designed in 2002 and consists of 1 000 primary sampling units (PSUs). The 2001 population census enumerator areas (EAs) were used as PSUs. These PSUs were drawn, with probability proportional to size, from a pre-census 2001 list of EAs provided by Statistics South Africa.
The Master Sample excludes special institutions (such as hospitals, military camps, old age homes, school and university hostels), recreational areas, industrial areas and vacant EAs. It therefore focuses on dwelling units or visiting points as secondary sampling units, which have been defined as ‘separate (non-vacant) residential stands, addresses, structures, flats, homesteads, etc.’
As the basis of the 2004 SASAS round of interviewing, a sub-sample of 500 PSUs was drawn from the HSRC’s Master Sample. Three explicit stratification variables were used, namely province, geographic type and majority population group.
Within each stratum, the allocated number of PSUs was drawn using proportional to size probability sampling. In each of these drawn PSUs, two clusters of 7 dwelling units each were drawn. These 14 dwelling units in each drawn PSU were systematically grouped into 2 subsamples of seven, to give the two SASAS samples.
Number of units: Questionnaire 1: 2 497 cases realised from 3 500 addresses; questionnaire 2: 2 483 cases realised from 3 500 addresses; combined : 4980 cases
Weighting
Data for the combined dataset is available with the individual weight (for analysis at individual level) as well as household weight (when analysis are done at household level).
The data were weighted to take account of the fact that not all the units covered in the survey had the same probability of selection. The weighting reflected the relative selection probabilities of the individual at the three main stages of selection: visiting point (address), household and individual.
Visiting points in the Northern Cape and KwaZulu-Natal were oversampled, because of the small population size in the former and a desire to ensure a large enough Indian/Asian sample in the latter. Because of this, weights had to be applied to compensate for the greater probability of being selected.
The resulting weight is called 'benchwgt' in the half samples and 'combiwgt' in the full sample. The sample is weighted to represent the South African population older than 16 years.
All analysis should be done on weighted data.