The structure of the survey is a continuous cross-sectional survey, each complete sample being covered in the course of two years. As well as keeping down the annual cost of the survey and making the volume of fieldwork more manageable, a continuous survey will, in time, enable national trends to be detected sooner than would periodical surveys.
The sample is being drawn from the small user file of the Postcode Address File (PAF). The overall design of the sample is to pursue a wholly random sample where fieldwork conditions allow - namely in areas of high population - and to cluster interviews in the remaining areas (also on a random basis).
To allow sufficient disaggregation of the survey results, an achieved sample of approximately 31,000 households over two years is required. The sample in each quarter is geographically representative so that statistically reliable results for Scotland as a whole are available for each quarter. In addition, the survey design is such that results are available for each of the larger local authorities (those with an achieved sample size of 750 interviews per year) each year, and for all local authorities, regardless of size, every two years.
The Highest Income Householder, or his/her partner/spouse, is interviewed face-to-face about themselves and other members of the household. In addition, a randomly selected adult member of the same household aged 16 or over (who may, by chance, be the same person) is interviewed on other topics. In this way, results from the survey are representative of both Scottish households and adult individuals.
Computer Assisted Personal Interviewing (CAPI) is being used to collect the survey data. This has a number of important advantages over 'pen and paper' interviewing techniques, including faster interviews, automatic edit checks and a quicker flow of information from the survey interviewer to the survey database.
Further details about the survey methodology can be found in latest technical report found on the Publications page. Older methodologies are also available.