Abstrak
RISKA, Reg No. 2030104056, thesis title “Analysis Mechanical Errors in Argumentative Essays Written by English Teaching Department Students at Uin Mahmud Yunus Batusangkar". The mechanical errors in writing, including spelling, punctuation, and capitalization mistakes, remain a common issue among English as Foreign Language students. This research aims to analyze the most common mechanical errors in argumentative essays written by English Teaching Department students at UIN Mahmud Yunus Batusangkar, particularly those who completed the comprehensive writing test in 2024. This research used descriptive quantitative method with document analysis technique as the main instrument. The research sample consisted of 31 argumentative essays that were analyzed based on the classification of errors using theories from experts that are in accordance with the problem under study. To ensure data validity, this study applied peer debriefing technique, while reliability was tested through inter-rater reliability technique. The findings reveal that capitalization errors (55,33%) are the most frequent, followed by spelling errors (27.16%) and punctuation errors (17.50%). These results indicate that students make errors in the application of basic writing mechanics, which affects the clarity and coherence of their essays. The study highlights the need for targeted instructional strategies, such as explicit teaching of writing conventions, proofreading exercises, and the integration of digital writing tools to enhance students’ mechanical accuracy.