Assessment not only gauges what students have learned, it shapes how many students approach learning. This means that the assessment methods used for groupwork can not only gauge student performance but, if well designed, also encourage students to contribute their best to the group. Therefore, assessing groupwork starts with aligning the topic aims, learning outcomes, and assessment.

Aim: To develop groupwork skills

Learning Outcome: Students will demonstrate the ability to work with others to achieve timely delivery of a product
(The product may be any type of assignment e.g. report, presentation, business plan, creative work etc.)

Assessment: Assess their ability to work in a group + assess the product

It is important to note here that the process of groupwork needs to be explicitly assessed as well as the product if groupwork skills are to be valued by the student.

There are many methods for assessing groupwork. Each has its pluses and minuses and requires careful consideration. Some methods may also work better for some tasks and group sizes than others. It is also possible to use a combination of these methods. For any of these methods, you will need assessment criteria. For further information on each of these methods, follow the link:

Collective marking 
There is no individualization of the mark so every member of the group gets the same mark.
Component marking
Every member of the group gets a collective mark for the product but each individual gets a separate mark for their group contribution.
Multiplier marking 
Each student in the group is assessed compared to the other members of the group. The product mark is then multiplied by this group contribution weighting.
Penalty marking
The group monitors the contribution of its members. If someone is not contributing, they are issued with a formal warning, a chance to improve, and a penalty if they do not improve.
Observer marking
An observer, e.g. the lecturer or tutor, monitors the group, observes the contributions that each member is making, and will base their mark on those observations
Individual marking
The students work as a group but each student is then assessed on an item of work that they produce by themselves.
Distributed marking
The lecturer/tutor awards a set number of marks for the product and lets the group decide how to distribute the marks between the members.

For further information on assessing groupwork see the following

Peer assessment of group work: a review of the literature

Assessing groupwork by University of Melbourne:

Supplementary Information about Self and Peer Assessment

Assessing Groupwork by the University of Sussex

The Assessment of Groupwork: lessons from the literature

Group assignments at Deakin University