A diagnosis of students' errors in answering the mathematics test in senior high school

This study aims to reveal: (1) the characteristics of a diagnostic test items used in the mathematics subject of class X SMA; (2) the degree of errors from several types of students’ errors in answering the mathematics test; and (3) the dominant factor causingthe studentsto make mistakes in answering mathematics test.This study used the quantitative approach. The population was established was the class X students of eight SMA’s in Mataram. The sample using the Proportionate Random Sampling technique. It consisted of 350 students for preliminary field testing and 450 students for main field testing. The research instrument was a mathematics diagnostic test, questionnaire and interview guidelines. The results showed that: (1) the diagnostic test instrument had met the qualitative and quantitatively content validity, proven empirically fit with the Partial Credit Model (PCM), a reliability index of 0.92 (high category), and all items in the diagnostic test instrument with the value of difficulty ranging categorized in moderate difficulty; (2) misrepresentation became the dominant errors if compared with misconceptions, the counting errors, and procedural errors, the errors that was dominant in the topic domain was Inequalities Linear System Two Variables if compared with Rational and Irrational Inequality 1 Variable, Equations and Inequalities of Absolute Value, and Linear Equations System 3 Variable; and (3) in term of the ability aspects needed by the students in answering test correctly, most of the students did not understand how to solve the problem of inequality, determining factor quadratic equations, determining the members of the set completion, the problems concerning graphs and to solve problems that required capability of language interpretation into the mathematics model.