1. A method for controlling transmission of feedback of mobile terminals receiving a multicast or broadcast service, the method being performed by at least one of the mobile terminals to reduce uplink traffic in a mobile communication system and comprising: receiving the multicast or broadcast service, receiving a parameter comprising a percentage subset of receivers based on which the mobile terminal decides whether to provide feedback, deciding whether or not to provide the feedback for the multicast or broadcast service based on the received parameter, and transmitting the feedback, wherein the feedback is used for statistical analysis, wherein: the deciding of whether or not to provide the feedback includes performing a probabilistic experiment, wherein the parameter indicates a success probability of the experiment.