Mathematical communication skills of SMP Negeri 3 Tolitoli students on set operations material in terms of mathematical ability. This type of research is qualitative research. The subjects of this study were selected based on their mathematical abilities. The subject was given a written test with set operations material and then interviewed. This study uses a triangulation method, namely by comparing the results of written tests and interviews. The results of this study are (1) Subjects with high mathematical abilities achieve three indicators of mathematical communication skills in set operations, namely being able to express mathematical ideas through oral and written; able to interpret and evaluate mathematical ideas both orally and in writing; and able to use terms, mathematical symbols to model mathematical situations or problems. ( 2) Subjects with moderate mathematical ability achieved two indicators of mathematical communication skills on set operations, namely being able to express mathematical ideas only through writing, and being able to interpret and evaluate mathematical ideas orally and in writing. (3) Subjects with low mathematical ability achieved one indicator of mathematical communication skills on set operations, namely expressing mathematical ideas in writing.

This study aims to describe the differences in students' misconceptions with field-independent and field-dependent cognitive styles. This research is a descriptive-qualitative research involving junior high school students in Palu city. The subject of this study consisted of two female students, having a field-independent cognitive style and field dependent. The results showed differences in the misconceptions of field-dependent and field-independent students, namely field-dependent students including: (a) misconceptions in the use of distributive properties and algebraic addition operations, (b) misconceptions of basic mathematical concepts in determining mathematical models in the form of equations, (c) misconceptions in applying the concept of equivalent equations. While, field-independent students only experienced misconceptions in applying the concept of equivalent equations. The causes of misconceptions filed-dependent are the initial concept of the wrong student, the stage of cognitive development of the student, students' associative thinking and intuition. While field-independent is associative thinking and intuition is wrong.