Peer assessment, done properly

Ask students to rate each other and you get something genuinely valuable: a view of contribution that no edit log can capture, like who led, who organised, who carried the meetings. You also get a set of well-documented biases. Whether peer assessment helps or harms depends almost entirely on how you set it up.

What it is good at

Peer marks are more reliable than their reputation suggests. Across many settings, peer assessment shows adequate reliability and validity, with learning effects comparable to teacher assessment. ¹ A meta-analysis comparing peer and teacher marks found they agree most closely when peers make global judgements against well-understood criteria, rather than scoring many separate dimensions. ² That single finding is the most important design instruction in this whole area: keep the judgement holistic and the criteria clear.

Where it goes wrong

The failure modes are real and specific. When scores count toward a grade, students become lenient, and the bias is larger among weaker contributors. ³ Friendship distorts scores too: students over-score peers in general, and closer friends are over-scored even more, an effect that persists even when a rubric is in place. ⁴ These are not reasons to abandon peer assessment. They are the things your design has to account for.

The bias you can stop worrying about

One fear is overstated. Reciprocity, the worry that students trade favourable ratings, turns out to be tiny in practice: with multiple raters it accounted for only about one percent of the variance in peer-assessment scores. ⁵ Use enough raters and the "I will rate you well if you rate me well" problem largely takes care of itself.

The design rules that follow

• 1.Keep the grade weight of peer scores modest, not decisive, to blunt leniency. ³
• 2.Ask for a short written justification, not just a number. ³
• 3.Keep ratings confidential, so students rate honestly. ³
• 4.Use clear shared criteria and favour global judgements over many fine dimensions. ²

Turning ratings into marks

The mature way to use peer scores is not as the grade, but as a weighting on the group mark. Open tools have done this for years: WebPA has each student rate teammates and themselves, 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 None of this is experimental; it is established practice.

How Dwixel handles it

Dwixel collects peer assessment confidentially, and students cannot read their own ratings, which is exactly the condition the research recommends. Crucially, it is treated as one signal among several, sitting alongside the objective contribution record and your own academic judgement, rather than being asked to carry the whole grade on its own.