Design

The aim of this study was to develop a reliable and valid test to measure student's conceptual understanding in science course of eighth grade and investigate the relationship between conceptual understanding and academic performance in science among eighth grade students. The research method is descriptive that performed via survey. The study population consisted of all secondary school eighth grade students in the academic year 2015-2016 in Darab city. Using multi-stage random sampling method, 396 students, including 189 girls and 187 boys were selected. To collect data, a tool called Eighth Grade Science Conceptual Understanding Test (EGSCUT) was made in collaboration with eighth grade science teachers. It consists of 15 multiple-choice questions that have been prepared according to the eighth grade science book. To evaluate the test questions, difficulty level and discrimination index was calculated. And to check the TEST validity, content validity, CVR (0.59) and confirmatory factor analysis were used. The results showed that the test is valid enough. The test reliability using internal consistency, Kuder Richardson 20 and split-half obtained 0.86 and 0.83 respectively. The result showed that “Eighth Grade Science Conceptual Understanding Test (EGSCUT)” was appropriate to assess conceptual understanding in science among eighth grade students and has required validity and reliability. As a conclusion, conceptual understanding of eighth grade students in science can be accessed via assessment of their ability to apply and use knowledge. In addition, results showed that there is a significant positive relationship between academic performance and conceptual understanding of science. When students learn content conceptually, they can apply them in new situations and respond appropriately to different questions.