In UX, the Between-subject design study is used to measure the efficiency of several interfaces (product iterations or related services) by a single study. The method regards testing only one interface by a single user. For instance, there are two e-commerce websites, A and B, and each of the users is assigned to check either A or B interface.
Unlike, the Within-subjects design study means checking all interfaces by the user, so the user is going to check both, A and B interfaces.
