Sample size
NMS
NMS
The combined sample size for the paper and push-to-web surveys was calculated to ensure that: 1) prevalence of key survey outcomes (e.g. health and care outcomes) could be estimated with adequate precision; and 2) a small difference in response rates could be detected between the paper and push-to-web surveys. Assuming women were randomised equally to the two survey arms and a baseline response rate of 29% (based on previous NMS, [