Omission Students’ Errors in Part B
in Indonesian. The passive form in Indonesian is marked by the presence of {di-} before the verb Moeliono, 1987: 280. Due to the transfer of language diperbaiki in
Indonesian, the student finally decided to put is before repaired. Moreover, Table 4.6 shows that the mixing of addition and misformation has
the highest number compared to other combinations in total errors. This can be observed from student’s answer in question 9.
Question 9 : We need to have someone check out our computer for viruses.
SA : Someone is had to be needed to check out our computer.
Student’s answer above has four types of mistakes. First, the student changed the sentence into regular passive voice. It can be observed from be is in the sentence.
The researcher tried to observe all the answers done by the student who wrote the sentence above. The result was the student changed the entire question into regular
passive voice. It shows that the student did not acknowledge the passive form of causative. In the other hand, the student only changed the sentence into what heshe
only knew about that was the form of regular passive voice. Second, the student misunderstood have causative in the sentence and
considered it as modal form of have to. It is probably because the word to have in the question that had tricked the student to think it as modal of have to. As the result, the
student changed it into the passive form of have to as modal: had to be needed. Third, the student put double be in the sentence: is and had. This kind of error
is called double marking which can be categorized as addition error Dulay, Burt, and
Krashen, 1982: 156. The student acknowledged that the question is in present tense so heshe wrote is as the be for the passive form. However, because heshe also
mistakenly considered to have as modal tense, heshe put had as the second auxiliary. Fourth, the student added the to-infinitive clause in the sentence: to check out
our computer. This can be resulted from the translation of the question in Indonesian as: Kami perlu menyuruh seseorang untuk memeriksa komputer kami dari virus.
Because the student added untuk in the translation, heshe added to-infinitive clause in the answer. In addition, there is also omission of we and for viruses. We is deleted
because the phrase by us is not necessary to be put in a passive form. Meanwhile, for viruses is deleted because student thought it just an adjunct, an additional information
for the sentence. From the analysis, it can be observed that the student had errors in
misformation and addition. Misformation error can be seen from the change of active causative into regular passive voice and the formation of have causative into have-to
as modal. Addition error can be observed from double marking error and the presence of to-infinitive clause in the answer.