All percentages cited in this report are based on weighted data. The weights applied to the SSA 2017 data are intended to correct for three potential sources of bias in the sample:
- Differential selection probabilities
- Deliberate over-sampling of rural areas
Data were weighted to take account of the fact that not all households or individuals have the same probability of selection for the survey. For example, adults living in large households have a lower selection probability than adults who live alone. Weighting was also used to correct the over-sampling of rural addresses. Differences between responding and non-responding households were taken into account using information from the census about the area of the address as well as interviewer observations about participating and non-participating addresses. Finally, the weights were adjusted to ensure that the weighted data matched the age-sex profile of the Scottish population (based on mid-year estimates from the National Records of Scotland).