Sample size calculation
The satisfaction score is a continuous score taking values between 0 and 10 points. To be able to show a minimum effect size of ¾, corresponding to a difference of about 23% of the overall score, for an estimated standard deviation of about 1.5 points, with a power of 80%, and considering a type I error rate of 5%, a number of 30 patients per group would be necessary. To take into account a rate of non-matchable patients of about 20%, as well as a rate of non-evaluable patients of about 10%, 40 patients will be included in each group, for a total of 80. Given the lack of preliminary data, and the uncertainty around the assumptions used for sample size calculation, an interim analysis will be performed after approximately half of the initially planned number of subjects has been included. The purpose of the interim analysis is to re-estimate the number of subjects needed based on the distribution of scores, in order to ensure sufficient statistical power of the study. Since no early ending is planned after the interim analysis, the alpha risk will not be adjusted, and the formal comparison between the two groups by hypothesis testing will be done only at the final analysis.