I have thought how I could know set up the time intervel for examining responsiveness. I think there are three ways to decide the time intervel.
1. Literature review: seeing the former research studies
2. I could recurit the small data from different time intervels, a pilot study, and analyze the responsivenvess from comparing different time intervels. Or I already have data on hand in several time intervals. I could analyze anc compare the data from time intervals, and then decide the better time interval.
3. Based on the clinical experience