In order to evaluate with accuracy complex cognitive performances of students (graduate students in this case), our research focuses, on the one hand, on self-assessment (based on criteria grids) and, on the other hand, on instrumented confrontation (graph with index calculations) of self and external assessments concerning a complex performance. This article presents an analysis of the degree of agreement found in the confrontation of these two judgements. It compares the assessment judgements (expressed by the student and by the teacher) based on a graphical representation of discrepancies, on numerical indicators and on justifications written by the student and by the teacher on the criteria grid. This type of individual analysis can be used to prepare personalized feedback for the benefit of the students. It was used in a university course as a basis for a formative discussion between the teacher and each student.