The fundamental purposes of this study were to describe the types and causes of errors of the students on making compound sentences. The research was conducted in XII Science class1 of SMAN 3 Pangkalan Bun 2013/2014 academic year. The types and causes of errors which analyzed werebased on the Dulai’s theory whichconsist of nine types of errors and four causes of errors. The processes of analyzing the errors made by students wereusing analysis steps based on Ellis’s theory.
The writer used quantitative approach and content or document analysis method. The research type of this research was descriptive research. In collecting the data, the writer used two techniques, namely: (1) test and (2) observation. Then for analyzing the data, the writer used several techniques, namely: (1) identifying errors, (2) describing errors, (3) explainingerrors, (4) errors evaluation. In categorizing the errors, the writer use (1) surface strategy taxonomy, and (2) comparative taxonomy. The sample of this study were 27 students who had studied about compound sentence material.
The result of this study isas follows: (1) from 27 students, there were 97 errors in making compound sentences. The errors were spread in 7 of 9 types of errors based on the Dulai’s theory. There was, 39 errors (40.21%) in misformation: alternating forms, 15errors (15.46%) in addition: simple addition,15 errors (15.46%) in misformation: archi-forms, 12 errors (12.37%) in omission: grammatical morphemes, 9 errors (9.28%) in omission: content morphemes, 4 errors (4.12%) in misordering, and3errors (3.09%) in addition: double markings. (2) Those97 errors made by the students categorized in 3 of 4 causes of the errorswhich are: others errors by 76 errors (78.35%), interlingual errors by 14 errors (14.43%), and developmental errors by 7 errors (7.22%).
The common types of error occurred by the students is misformation: alternating forms, and the common causes of errors occurred by the students is other errors.