As much as we may want to incorporate group work into our courses, often they can be a difficult beast to manage, particularly when it comes to assessing the contribution of each group member to the assignment. If you are concerned that not all group members are contributing equally, this article has five suggestions that you might want to try: http://www.facultyfocus.com/articles/effective-teaching-strategies/students-riding-coattails-group-work-five-simple-ideas-try/?ET=facultyfocus:e122:351846a:&st=email
If you are doing group work on Blackboard, one of the great suggestions I just learned about is the Participation Summary option. This tool allows you to see which students have contributed the most to the project, perhaps a wiki. It will actually tell you what percent of the content was completed by particular students. No more guess work!
You can read more about this function here: https://help.blackboard.com/en-us/Learn/9.1_SP_12_and_SP_13/Instructor/060_Course_Tools/Wikis/040_Grading_Wikis
Thanks, Jamie, Jim, and Val.