This research examines errors in writing by the eleventh grade of
public high school students in Boyolali in the academic year of 2022/2023. The
aims of this research are: (1) to describe types of students’ grammatical errors
in their writing, (2) to determine the percentage of errors in each type of
students’ writing error, (3) to describe the most common type of students’
grammatical errors in their writing, (4) to describe the least common type of
errors made by students in their writing, and (5) to describe the causes that can
influence some students’ grammatical errors in theirwriting. This study used a
qualitative descriptive method and the data were collected through writing test
and questionnaire. The data were analyzed using an error analysis approach,
which involves the following steps: collecting the sample, identifying errors,
describing and classifying the errors based on the error types, explaining errors,
and evaluating errors. The result shows that there are four types of errors:
omission, addition, misformation, and misordering.Thus, there are 310 errors in
totals. The most common error is omission with the percentage of 53.22% (165
errors). The least common error is misordering with the percentage of 7.74% (24
errors). The causes of errors are: overgeneralization, ignorance of the rules of
restriction, incomplete application of rules, and false concepts hypothesized.
This study can be utilized by teachers to emphasize on how to correct the most
frequent errors that students made. Thus, the teacher should develop effective
learning strategies in order to improve students’ overall writing skills.