Sample size
We used HyLown Consulting (2019 HyLown Consulting LLC, Atlanta, GA) to calculated the sample size. Under the assumption that the accuracy in the self-driven training group would be 70% compared with 78% in the didactic group, a sample size of 481 observations was needed to detect this 10% difference in accuracy between the two groups with 80% power and alpha of 0.05, given that we had 20 cases for tests and a drop rate of 0.05. A sample size of 26 trainees in each group was needed.