Research Hypotheses THEORETICAL FRAMEWORK

to measure the students’ critical thinking skill as the samples of this study were twelfth grade students. This test was considered suitable to be used in the present study because it is claimed by its developers to be a general critical thinking test which attempts to measure the critical thinking skills as a whole and it is best used for grade 9 to 12. Level X includes the following skills: induction, deduction, credibility, and identification of assumptions see the instrument in Appendix 1. Moreover, the test has been widely used throughout the world more than twenty years to measure critical thinking skill. Additionlly, level X was chosen by several researchers Rosyanti and Rosna Awang: 2008, Rozaidi Ismail: 2003 to measure students critical thinking skills. The CCTT was already being tested in the term of validity and reliability. The developers argue for the construct validity of the CCTT based on its content validity. The test was developed based on a sound rationale and that the test items were intensively discussed by the test developers who were scholars involved in the Illinois Critical Thinking Project. Meanwhile, the developers claimed that the reliability coefficient of the CCTT Level X ranges from .67 to .90. 3 2. Instruction to write Argumentative Essay This test was conducted to measure the students’ argumentative writing skill. There were three topics given to develop by the students see the instrument in Appendix 2. The topics were adopted from the students textbook Aim High 6 and Contextual English. In assessing writing, the assessment rubric which was adopted from the book entitled Assessing Writing was applied in this study. It was developed by Jacob et al, and cited by Sara Cushing Weigle in her book. There were five categories to be assessed include; content, organization, vocabulary, mechanic and usage see the assessment rubric in appendix 3. To validate this scoring scheme, two raters were asked to analyze the proposed components, as well as the sub-components. Then, they were required to 3 Ennis, op. cit., p. 3. score the students argumentative writing by using assessment rubric. The raters were the English teachers of SMA Kharisma Bangsa and the researcher herself.

E. Technique of Data Collection

Before collecting the data the researcher rechecked to make sure that the students were ready to do the test. The first test that was being administered was critical thinking test and continued by argumentative writing test. 1. The Steps of Critical Thinking Test a. Firstly, the participants were asked to fill out the name, date of birth, grade and students’ number in the answer sheet. b. The participants were asked to read the direction of the test c. The researcher explained the direction of the test and how to answer the test. After the participants were ready, the test was started and the researcher supervised the test took place. d. The participants had to finish 71 questions of critical thinking test in 50 minutes. e. After the participants completed the test, the participants’ answers were scored and the results were analyzed. 2. The Steps of Argumentative Writing Test a. The writing test was conducted in the same day directly after the participants finished the critical thinking test. b. Firstly, the participants were asked to fill out the name, date of birth, grade and students’ number in the answer sheet. c. The participants were asked to read the direction and the scoring criteria of the test. d. The participants were free to choose one from the 3 topics given. e. The students were asked to write argumentative essay in 30 minutes with the length of the essay was at least 250 words. f. After the participants finished the writing test, their writings were scored and the results were analyzed by using assessment rubric.