 Sample size To calculate the necessary sample, we considered the difference in medians observed in a previous study in the same population Raurell-Torredà M, Olivet-Pujol J, Romero-Collado A, Malagon-Aguilera MC, Patiño-Masó, J, Baltasar-Bagué A. Case-based learning and simulation: useful tools to enhance nurses education? Non-randomized controlled trial. J Nurs Scholarsh. 2014, Oct 25. doi: 10.1111jnu.12113. The standardized median difference was 0.9 points. With the aim of obtaining the same difference in the present study, accepting an alpha risk of 0.05 and beta risk less than 20 in a two-tailed test, the estimated sample size 21 scenarios in each arm of the study. 