THE EFFECT OF TEACHING METHODS AND GRAMMATICAL ABILITY ON STUDENTS ACHIEVEMENT IN WRITING EXPOSITION ESSAY

The objectives of this experimental research were to investigate whether: 1) students achievement in writing exposition essay taught by using Content-Based Instruction (CBI) method was higher than taught by using Task-Based Language Teaching (TBLT). 2) Students achievement in writing exposition essay with high grammatical ability was higher than those students with low grammatical ability and 3) there was interaction between teaching methods and grammatical ability on students achievement in writing exposition essay. The population of this research was the students in grade XI science of SMA Negeri 1 Kisaran in 2012/2013 school year. The total number of population of this research was 240 students and 80 students were selected as sample of this research by applying cluster random sampling. The research design was experimental research by using factorial design 2x2. The first class was taught by using Content-Based Instruction (CBI) method and the second was taught by using Task-Based Language Teaching (TBLT). Grammatical Ability test was conducted for classifying the students upon the high and low grammatical ability. Students achievement in writing exposition essay was measured by using writing exposition essay test. The data were analyzed by applying two-way analysis of variance (ANOVA) at the level of significant &#8733;=0.05. The results of the data analysis proved that: 1) CBI and TBLT methods significantly affect students achievement in writing exposition essay (sig. = 0.013 < 0.05), students achievement in writing exposition essay taught by Content-Based Instruction (CBI) method is higher than students achievement in writing exposition essay taught by Task-Based Language Teaching (TBLT) method (78.55 > 72.87), 2) Students achievement in writing exposition essay with high grammatical ability was higher than those students with low grammatical ability(77.25 > 74.17), and 3) there was interaction between teaching methods and grammatical ability on students achievement in writing exposition essay (sig. = 0.00 < 0.05). Moreover, Tuckey-Test result also showed that students with high grammatical ability got higher achievement if they were taught by using CBI method while students with low grammatical ability got higher achievement if they were taught by using TBLT method.