Applying Cooperative Learning To Develop Vocabulary Mastery Of Grade 7 Students

This study aims at proving whether applying cooperative learning has significant effects to develop the students\u27 vocabulary mastery or not. It employs a quasi-experimental design. One group became an Experimental Group and the other was a Control One. They were tested twice by giving pretest before treatment and posttest after treatment. The sample of this research was selected by applying convenience sampling. Based on the result of the experimental group, the mean score of posttest is 79.76 and the pretest 71.31. Whereas, the control group\u27s mean score of posttest is 76.41 and pretest 74.53. Furthermore, It is also proven through the value of the t-counted (2.044) is greater than the t-table value (1.671), it means that the cooperative learning is effective to apply in teaching English to develop the students\u27 vocabulary mastery