Influence of group size on students' participation in online discussion forums

► This study examines students' interactivity in discussion forums in an online course. ► It examines the frequency and interactivity level of participation in discussion forums with different modules of group size. ► Class guidelines and active encouragement work to increase students' overall participation. ► Class-size discussion module has its limitations in promoting a higher level of interactivity among students. ► Small-group discussion module is superior in terms of promoting quantity and quality of participation than class size.