Maternity care survey 2018: technical report

3. Sample Design

A review into the sampling methodology was carried out in advance of the 2018 survey. Full details of the review, including the final sampling methodology used for the 2018 survey, are provided in the Sampling Review Paper which can be found at www2.gov.scot/Resource/0054/00541965.pdf.

Statisticians in Scottish Government calculated the sample sizes for each strata to ensure results could be provided at NHS Board and hospital level where possible. This information was then passed to NRS who generated the sampling frame from the Birth Registration Records and drew a sample.

Women eligible to be included in the sampling frame were those who had given birth between 1 February and 31 March 2018, who were aged 17 or over at that date and who were resident in Scotland. Women who had either lost a baby or had died were removed from the sampling frame. Women who had given birth to more than one baby were only eligible for sampling once.

The sample size calculated for each strata was based on the minimum number of responses that would be required to achieve an estimate that has a 95% confidence interval with width +/- seven percentage points, sampled from a finite population. The sample size was adjusted upwards to allow for assumed non-response based on response rates for the 2015 survey. For strata where the calculated required sample size is greater than the number of eligible women, all women were sampled.

A total of 7,782 women were included in the sampling frame and a total of 5,165 women were sampled to take part. 

Access to Individuals’ Names & Addresses

Approval was given by the Public Benefit and Privacy Panel (PBPP)^[5] to use Birth Registration Records to identify a survey sample and approach individuals. A copy of the approval letter is available at www2.gov.scot/Resource/0053/00535552.pdf.   

Data transfers containing individuals’ names and addresses were done securely and were limited to the variables required to mail the survey pack to the individual. All data was accessed, managed and stored in accordance with the data confidentiality protocols described in the privacy notice for the survey^[6].