The Van Hiele is a learning model that offers different types of thinking which students experience, when faced with geometric shapes. It includes the stage of visual encounter with the geometric shape, to the formal perception of geometrical proof. Misunderstandings can cause confusion and failure of students to solve problems. Sometimes, because of the interrelated nature of mathematical concepts, misunderstandings cause problems in the future learning of students. The purpose of this study was to identify the misconceptions of 8th grade students in geometrical skills and its related subjects. It also intends to use Van Hiele's theory to improve geometrical skills of the students. The statistical population of this study included 8th grade male students, at junior high schools, in the first district of Sanandaj educational department in the academic year of 1395-96. The sample consisted of 318 students who were selected by random cluster sampling method. Regarding its purpose, this study was applied, and in terms of its implementation, it was descriptive and a kind of field study as well. The measuring scale of this study consisted of written tests. Cronbach alpha coefficient was 0/896. The result of this research showed that most students had many various errors in geometry and its related subjects. The mean score of students in the experimental group was lower than that of the control group in terms of the misconception. There was a significant difference between students’ performance at the control and experimental groups at Van Hiele's thinking level. This difference was in favor of the experimental group students. There was also significant difference at 0/05 level between students at both groups in geometrical skills and this difference was in favor of the experimental group, as well.
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