Peer assessment is a form of co-assessment in which a student's work is analysed and evaluated by their fellow students. To carry out the assessment, students use a rubric prepared by their teachers. For assessment to be fair, students need to be engaged to be effective in the process, but teachers also need to provide clear and appropriate assessment rubrics.

We have carried out an experience of peer assessment with students in the 1st year of dentistry at the University of the Basque Country UPV/EHU. To do this, we used the Moodle workshop tool, which allows each student to be assessed by several of their classmates, integrates these assessments and assigns a grade to the work.

Thirteen workshops have been conducted over the course of the year, with different characteristics that we group into these modalities:
- Writing: free-text response to a question.
- Drawing: free execution of an illustration.
- Drawing interpretation: pointing out the structures represented in an illustration.
- Closed answer: there is only one possible answer (one word).
- Mixed closed answer/writing: combination of both types of exercises, i.e. one part with only one possible answer and a free text part.
- Mixed writing/drawing: combination of a free-text response and the realisation of an illustration.

To check the quality of the assessments carried out, we compared the grades awarded by Moodle after corrections by classmates with the grade awarded by the professor using the same rubric. We analysed the distribution of this difference between the workshop modalities carried out. The statistical analysis indicates that there are significant differences between the modalities. In particular, the comparison by pairs of modalities indicates that the Drawing modality differs from the rest of the modalities. These results are similar to those we ourselves obtained in a previous experience.

Our results indicate that the quality of peer assessment may depend on the type of exercise performed. This is probably conditioned by the type of rubric associated with each modality of exercise.

Keywords: Peer assessment, Moodle, Workshop, rubric.