Grading group work you can defend

The goal of assessing group work is not to catch people. It is to give each student a mark that reflects what they did, and to be able to explain that mark if they ask. Both halves matter, and they need different things.

Peer assessment is useful, and partial

Student peer marks can track teacher marks reasonably well, especially when peers make global judgements against criteria they understand rather than rating many fine-grained dimensions. ¹ Peer assessment shows adequate reliability and validity across many settings. ² Some feared biases are also smaller than assumed: with multiple raters, reciprocity (rating a teammate well so they return the favour) accounted for only about one percent of the variance in scores. ³

But peer marking has real limits. Scores inflate when a grade is attached, and friendship bias persists even with a rubric in place. ^{4 5} The lesson is not to discard peer assessment. It is to design it carefully (low grade weight, written justification, partial anonymity) and to never make it the only thing the assessment can see. ⁴

Established practice: weight the group mark by contribution

The mature approach in the literature is not to grade everyone the same and is not to grade everyone separately. It is to individualise a group mark using peer-assessed contribution. Open tools have done exactly this for years: WebPA, developed at Loughborough University, has each student rate teammates and themselves and then moderates the overall group mark into individual marks. ⁶ Instruments such as CATME formalise the dimensions of team-member effectiveness with validated scales. ⁷ This is settled practice, not novelty.

Where objective traces come in

Peer judgement answers "how did this person work with us". It does not, by itself, show how much of the artifact each person actually produced. That is what an attributed contribution record adds: a second, independent signal grounded in the work itself rather than in opinion. Used together, the two cover each other’s weaknesses. Peer ratings catch the things traces miss (coordination, ideas, leadership); traces catch the things ratings distort (who actually wrote it). Dwixel keeps the two separate and visible rather than blending them into one unexplained number.

Defensible means it survives an appeal

A mark is only as strong as the record behind it on the day a student challenges it. When work is handed in through Dwixel, every member signs off and the artifacts are frozen into a locked, timestamped snapshot, alongside the contribution picture at that moment. If the grade is later questioned, you are not reconstructing events from memory. You are pointing at a fixed record of what was submitted and who did it.