The impact of a rubric and friendship on peer assessment: Effects on construct validity, performance, and perceptions of fairness and comfort

• The impact of a rubric on peer assessment construct validity was investigated.
• Along with the impact of friendship between the assessor and assessee.
• 209 bachelor students, of which half used a rubric to peer assess a concept map.
• All students over-scored, but peer assessment with a rubric was more valid.
• When using a rubric, a higher level of friendship resulted in more over-scoring.

Construct validity of peer assessment (PA) is important for PA application, yet difficult to achieve. The present study investigated the impact of an assessment rubric and friendship between the assessor and assessee on construct validity of PA. Two-hundred nine bachelor students participated: half of them assessed a peer's concept map with a rubric whereas the other half did not use a rubric. The results revealed a substantial reliability and construct validity for PA. All students over-score their peers’ performance, but students using a rubric were more valid. Moreover, when using a rubric a high level of friendship between assessor and assessee resulted in more over-scoring. Use of a rubric resulted in higher quality concept maps for peer and expert ratings.