Sample size and statistical analysis
The target sample size for this trial was 40 (20 per group), based on the weekly number of women attending who could be approached (15) and an estimated 60% participation rate. There were no prior estimates of standard deviations available for power estimation. All data was entered into a secure database and anonymised using participant codes at the point of data entry.
Statistical analysis was by intention-to-treat including all randomised participants, using R software Version 3.5.1 (Feather Spray). Continuous data were summarised as mean and standard deviation, and categorical data as counts and percentages. Between-group differences were reported with 95% confidence intervals (CI) and p-value (using t test to compare normally distributed data). Cohen’s d, difference in scores measured on a standard deviation scale, was used to determine effect size with values above 0.7 considered to be large33. Linear regression was used to estimate difference in continuous outcomes between groups post-procedure, adjusting for stratification factors (of menopausal status and parity) and baseline score.