The purpose of this study was to analyze the types of errors and causal factors that students do in solving story problems on the material of arithmetic sequences and series based on Newman. The type of research used is descriptive research with a qualitative approach. This study was conducted at Senior High School 1 Cigugur. The research subject consisted of students, with high ability students, medium ability students, and low ability students. The subject were taken using purposive sampling technique. Data collection techniques using test sheets, interviews, and documentation. Test the validity of the data using triangulation technique. The result of this study showed the percentage of errors in general was , with reading errors, comprehension errors, transformation errors, process skill errors and encoding errors. The causes of comprehension errors in students with medium ability is that they do not understand arithmetic sequences correctly, and they rush to do test questions because of limited time, while in students with low ability because from the beginning they do not understand the meaning of the questions given. The cause of transformation errors in students with low ability is that they do not know the formula/method used. The cause of process skill errors in high ability students is that they do not understand prioritizing bracketed operations and they rush to do the test questions so that they are not checked again, while in medium and low ability students in the previous stage (comprehension and transformation) they make mistakes. The cause of encoding errors in low ability students is lazy to write conclusions.

Keywords: arithmetic sequences and series, error analysis, mathematics education, newman, research and develovment mathematics education, story problems.