Abstrak
WULAN USPITA, NIM 2130104076, thesis title: "THE REASONS OF USING CODE MIXING BY STUDENTS DURING PROPOSAL SEMINAR PRESENTATION (Study of the English Teaching Department Students of UIN Mahmud Yunus Batusangkar 2024/2025 Academic Year)" English Teaching Department, Faculty of Tarbiyah and Teacher Science, Mahmud Yunus State Islamic University Batusangkar. The problem in this research is that the reasons why students' used code mixing in question and answer session of proposal seminar presentation have not been revealed. The aims of this research is to find out what the reasons are the students' used code mixing in question and answer session during proposal seminar presentation at UIN Mahmud Yunus Batusangkar in the 2024/2025 academic year. This research used qualitative research methods using qualitative descriptive design. The informants of this research are six students of English Teaching Department who already folloewd proposal seminar at UIN Mahmud Yunus Batusangkar in 2024/2025 academic year. The informants of this research were selected using purposive sampling technique. In this research, the researcher acted as a key instrument and used Interview guidelines and voice recorder. The technique of data collection in this research was to conducted an interview technique. The interview was conducted directly. To test the validity of the data, researcher used triangulation techniques. Furthermore, researcher used Miles and Huberman's interactive model data analysis technique which includes data reduction, data display, and data verification and conclusions. The results of the research shows that there are five reasons students use code mixing in question and answer session of proposal seminar presentation: 1) Afraid of Making Mistake, 2) Intention of Clarifying the Speech Content for The Interlocutor, 3) Repetition Used of Clarification, 4) Limited of Vocabulary and 5) Talking About Particular Topic.