Sample Size Calculation

The study design was a non-inferiority trial and for calculating the sample size, results of a similar study (Matan Elami-Suzin et al., 2013) [14] were considered. These authors showed that the abortion rate using mifepristone followed by misoprostol or oxytocin for the second-trimester abortion was 100% and 95.8%, respectively. Assuming that similar success rates would be obtained for the present study, a difference of 2% between the groups is clinically negligible, with the 5% level of significance (one-tailed) and power of 80%, a sample size of 60 in each group was considered to be sufficient to prove equivalence. The sample size calculation was done using the R-software version 3.24.