Advantages:

Allows for immediate responses to specific questions. Group study can be very effective when students immediately compare their notes between or after classes to see if they have similar comments about information presented in class.

On the other hand, some students may prefer to speak first with the lecturer for the clarification of questions and concepts (which can be done between class breaks, after classes, during the lecturer’s office hours or via email). This first hand information can then be shared with the group. Moreover, information obtained on the web by students to enhance their understanding of class readings and assignments should be recorded and shown to the lecturer for validation. Rationale, the information source on the web may be outdated, newer terminology may be in use and the authenticity of the information may be questionable.

Groups can also be very effective if the students first study their notes and get together in groups twice a week to reinforce the didactic material.

Finally, the student or students can get constant support and encouragement from fellow group members as well as the sharing of information or the development of wild and racy mnemonics to help to reduce the anxiety for mastering the assigned material.

Disadvantages:

Group size is important: I think that problems tend to occur with the effectiveness of group study if the group contains more than five students. Just consider the side chatter that can occur between students who are studying together.

Nonetheless, these distractions can in effect get out of control when the group contains a very large number of students. To exercise control, someone would have to take charge in the group and egos may be bruised in the process. In fact, the person taking charge must be diplomatic as well as make meaningful academic contribution to the learning process. The leadership can become democratic, if each student in the group has an opportunity to be the group leader.

Unfortunately, not all members will contribute "equally" to the discussion and in fact some group members may not have prepared or completed their "assignments".  Additionally, some members are poorly prepared and do make earnest attempts to understand the material, in which case they will use the group for extra tutoring.