Abstrak
Vocabulary plays an important role in helping students to understand English better. Therefore, vocabulary materials had to be well designed and taught to engage students in learning English vocabulary. Some problems found were; First, students had difficulty in learning vocabulary, Second, students were not equipped with English language learning when studying at the elementary school level. To overcome this research, the researcher used a strategy to improve students' vocabulary mastery. Vocabulary self-collection strategy (VSS) was chosen because it helped the growth of vocabulary knowledge and increased students' enjoyment of learning. This study aimed to determine the effectiveness of using the Vocabulary self-collection strategy to improve students' vocabulary mastery in learning English. This study used a pre-experimental design, with one group pretest and posttest design. The population was 8th-grade students of SMP Negeri 1 Matur with a sample consisting of 18 students. This study used a total sampling technique in sampling because the population was only one class. Data were collected using an instrument in the form of a vocabulary test in the form of 20 multiple-choice questions. The data were analyzed by a paired sample test of pre-test and post-test scores using SPSS 20. In this study, the results of hypothesis testing showed that Sig. (P-value) or Sig.(2-tailed) was 0.000, less than α = 0.05. It means that Sig. (P-value) 0.05, so it could be concluded that the alternative hypothesis (Ha) was accepted, or it could be said that the Vocabulary Self-collection strategy had a significant effect on improving students’ vocabulary mastery at 8th grade of SMP N 1 Matur. It was also proven by the average score of the post-test being higher than the average score of the pre-test. Furthermore, this study showed that after using VSS, students' vocabulary mastery was better than before the use of VSS. It could be concluded that this strategy was one of the good strategies for teaching vocabulary.