Dear professors,

If I want to explore the effects of mobiled assisted language teaching on students' performance, how can I ensure I spent the same time in teaching the experimental group as well as the control group, cause it is very convenient for students to interact with teachers through mobile devices after the classes. So if the control group is given the same extra time without mobile devices, their performance still may be enhanced. Then how can I get a conclusion to say there is significant effects on the experimental group's performance?