Hypotheses REVIEW TO THE RELATED STUDY

61 through experimentation, cause and effect relationship can be identified. The purpose of experimental study is to investigate the cause and effect of a certain condition. Considering the explanation above, related to this study, the writer used an experimental study because the aim of this study is revealing the effect of teaching materials and learning motivation towards students‟ writing skill. It involves three kinds of variables. The first variable is independent variable. In this study, the independent variable is teaching materials. It is also recognized as an experimental or treatment variable. They are two teaching materials that are used in this study, namely computer based communication teaching and textbook teaching. Both of these materials are used differently for groups of students at the first semester of Grade XI of SMAN 5 Yogyakarta in the academic year of 20152016. Fraenkel and Wallen 1993: 242 also explain that in the experimental research, it is important to make comparison group because it serves the purpose of determining whether the treatment has had an effect or whether one treatment is more effective than another. In this study, the group that received computer based communication is the experimental group and the group that received textbook material is the control group. The second variable is a dependent variable. The dependent variable in this study is writing skill of the students at the first semester of Grade XI of SMAN 5 Yogyakarta as the advanced level students. In 62 short, considering the explanation above, this experimental study used two groups, namely experimental group and control group. The third variable is a secondary independent variable. It is selected to determine if it affects the relationship between the primary independent variable teaching materials: computer based communication and textbook and motivation. In this study, learning motivation as the last variable that was labeled with two different names, i.e high learning motivation and low learning motivation.

C. Research Design

In this study, the writer used a factorial design to extend the number of relationships that examined. Fraenkel and Wallen 1993: 255 propose that they are essentially modification of either the post test only control group or pre test-post test control group designs, which permit the investigation of additional independent variables. As an experimental study, there are at least two groups in this experiment, namely control group and experimental group. The control group is the class that is taught by using textbook and the experimental group is the class that is taught using computer based communication. They were given different treatments. After the treatment, the groups were given a post test. In addition, before the treatment, the writer also gave a questionaire about learning motivation. The students‟ learning motivation is classified into high and low. By so doing, the writer