Sample size {14}
SECONDARY
We calculated the sample size needed for comparison of means between selected arms as detailed in the trial design. This was done independently for the primary and secondary outcomes based on the score of each questionnaire scale, upon which we selected the most conservative sample size for our study.The sodium questionnaire consists of 8 questions, each comprising a different number of items. In total, the participants can score up to 30 points by correctly answering all of the items in the questions. As this is a new questionnaire, there is no prior information on the average score and its variability in the general population; thus, the effect size cannot be directly estimated. In addition, we assume that a consistent change in knowledge through watching an animated video could be achieved by watching the video not only once, but several times. As our study provides a one-time view of the video and measures the effect afterwards, we aim to measure a small change in the average score, presuming that these small changes could turn into larger ones by watching the video again. Thus, we power the trial to detect a small effect size for comparing the mean score between samples, i.e., 