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HOW DOES THE COMMUNITY CARE? PUBLIC ATTITUDES TO COMMUNITY CARE IN SCOTLAND
ANNEX 2001 SCOTTISH SOCIAL ATTITUDES SURVEY TECHNICAL DETAILS
SAMPLE DESIGN
Sampling for the survey involved three separate stages of selection: selection of sectors, addresses and individuals:
1. At the first stage, postcode sectors were selected systematically from a list of all postal sectors in Scotland. Before selection, any sectors with fewer than 500 addresses were identified and grouped together with an adjacent sector. Sectors were then stratified on the basis of grouped council areas 6, population density (with variable banding used, in order to create three equal-sized strata per sub-region) and percentage of household heads recorded as employers/managers (from the 1991 Census). Ninety-six postcode sectors were selected, with probability proportional to the number of addresses in each sector.
2. Thirty-one addresses were selected at random in each of the 96 sectors. In some places more than one accommodation space shares an address. The Multiple Occupancy Indicator (MOI) on the Postcode Address File shows whether this is known to be the case. If the MOI indicated more than one accommodation space at a given address, the chances of the given address being selected from the list of addresses was increased to match the total number of accommodation spaces. As would be expected, the majority of MOIs had a value of one (94 per cent of those where an interview was obtained). The remainder, which ranged between three and 18, were incorporated into the weighting procedures (described below). In total the sample comprised 2976 addresses and each sample point issued to interviewers contained 31 addresses.
3. Interviewers called at each selected address, confirmed its eligibility, and, where an address was eligible, listed all residents eligible for inclusion in the sample - that is, all persons currently aged 18 or over residing at the selected address. The interviewer then selected one respondent using a computer-generated random selection procedure.
WEIGHTING
First, because addresses were selected using the Multiple Occupancy Indicator (MOI), weights had to be applied to compensate for the greater probability of an address with an MOI of more than one being selected, compared to an address with an MOI of one. Secondly, data were weighted to compensate for the fact that dwelling units at an address which contained a large number of dwelling units were less likely to be selected for inclusion in the survey than ones which did not share an address. (This procedure was used because in most cases these two stages will cancel each other out, resulting in more efficient weights.) Thirdly, data were weighted to compensate for the lower selection probabilities of adults living in large households compared with those living in small households. All weights fell within a range between 0.0524 and 4.6130. The weighted sample was scaled down to make the number of weighted productive cases exactly equal to the number of unweighted productive cases.
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