Scottish Surveys Core Questions 2022

1.4 Confidence Interval Calculations

All three source surveys are stratified to ensure sufficient sample sizes in smaller local authorities. SHeS is clustered in each annual fieldwork period and, while this effect cancels out over each four-year period, must be accounted for in producing annual results.

Confidence intervals have been calculated using a method to account for stratification and clustering (surveyfreq in SAS). In the case of negative lower confidence interval limits, values were replaced by 0 as population percentages always range between 0% and 100%. Confidence intervals across all subgroup estimates in SSCQ are provided in the accompanying Supplementary Tables in the Supporting Documents section.

Confidence intervals (at a 95% level) are plotted on point estimates for all charts and figures in the tables and reports. If the intervals surrounding two different point estimates do not overlap, then there is a significant difference between the two points. However, if they do overlap, it does not necessarily mean there is no significant difference (see further guidance).

A comparison of estimates of key variables across the three constituent surveys and the SSCQ are provided in Annex A.