Abstract
The present descriptive study aims to analyze the misconceptions among prospective mathematics teacher on geometry using three-tier diagnostic tests. The research subjects were 52 students of mathematics education study program in a university in Mataram, Indonesia. The data were collected from students' written work in solving the three-tier geometry test. The test investigated the students' (1) understanding of concepts, (2) reasons, and (3) confidence in answering problems (1) and ( Data analysis performed quantitatively and quantitatively using descriptive method. The results showed that there are: (1) 28.6% students who understood the concept, (2) 10.8% students who only guessed or were not sure of the answer and (3) 60.6% students had misconceptions. Misconceptions that occurred in students can be divided into three categories, namely: (1) pure misconceptions as much as 43.7%, (2) false positives (understanding deficiency) as much as 9.8%, and (3) false negatives (less information or careless) as much as 7.1%. The study implies many attempts are needed to improve prospective mathematics teachers' conceptual understanding in geometry.