This image represents the level of knowledge of students, measured by the performance on the course quizzes. It uses the students' performance on quizzes to assess the students' understanding of the subject. The students are mapped onto the x-axis and the concepts are mapped onto the y-axis of the matrix. The performance values are mapped onto the colour of the mark corresponding to a student and a concept, which is represented with a square. If a student has not attempted to answer questions related to a concept, the corresponding cell is left blank. The matrix enables global analysis of the overall performance of students on the course topics and comparison between topics. An extended description of the domain (particularly, association between concepts of the course with questions in quizzes) is necessary to produce this image.