49 with purposive sampling, that explain sampling is based on a specific purpose. So, in
this research sample is chosen based on purposive sampling technique. The sample in this research taken from population. A sample is a small subgroup
chosen from the larger population
47
. Frankael states that sample is any part of a population of individuals on whom information is obtained.
48
After known the score of interrogative sentences that given by the English teacher, in this research the
resarcher chose the class that got a lowest score to be analyzed, the researcher chose class VIII.E as the sample of the research.
D. Data Collecting Technique
Data collecting technique is the first main step in the research, because the main purpose of the research is to get the data.
49
In order to know student‟s errors in transforming from declarative into interrogative sentences, the reseacher used
documentation to collect the data. Document has some variations, personal and formal form. The example of personal form are picture, personal diaries, and personal
letter. The example of formal form are examination score, result of the report, and
47
Kenneth S. Bordens, Bruce B. Abbott, 2008. Research Design and Method A Process Approach 8
th
Edition . New York,.Mac Graw-Hill, p.163
48
Jack R. Fraenkel. 2009. How to design and evaluate research in education. New York: McGraw-Hill. p. 105
49
Sugiyono, 2008, Metode Penelitian Pendidikan Pendekatan Kuantitatif Kualitatif dan RD:
Bandung, Alfabeta, p.306
50 official letter.
50
In this research, the reseacher asked the students to transform thirty declarative into interrogative sentences based on the sentence provided.
E. Instrument of the Research
An instrument is a device to get the data.
51
In this case, the researcher used documentation as instrument in collecting the data as well. Research instrument was
one of important things that keep the quality of the research result. It means that if the research instrument was good, it got a good result. Therefore, research instrument
became important tool in this research. The researcher asked the students to transform thirty declarative into interrogative sentences used as documentation.
The instruction in doing documentation follows the steps: The researcher had given 30 sentences in declarative form to the students, and then students should transform
to interrogative form. They must finish them in 70 minutes. After that the researcher analyzed the errors that made by the students with Surface Strategy Taxonomy.
F. Credibility and Transferability of the Research
