Kholily Fatimah. K2214030. A Correlation Study between Vocabulary Mastery, Self-Efficacy, and Writing Skill of 3rd Semester Students of Sebelas Maret University in the Academic Year of 2020/2021. Thesis. Surakarta. Teacher Training and Education Faculty. Sebelas Maret University. 2020.

The aim of this study is to find out the correlation between: (1) vocabulary mastery and writing skill; (2) self-efficacy and writing skill; (3) vocabulary mastery and self-efficacy towards writing skill.

This study used correlational research which is a kind of quantitative research. The population of the study is the third semester of Sebelas Maret University in the academic year of 2020/2021. The samples are 20 students of class B2 that were chosen by cluster random sampling. The instruments which were used to collect the data were tests and questionnaire. The tests were used to collect the data of vocabulary mastery and writing skill. Meanwhile questionnaire was used to collect the data of students’ self-efficacy. The techniques used to analyze the data were Pearson Product Moment and Multiple Correlations.

The results of this research show that: 1) there is a positive correlation between vocabulary mastery and writing skill (rx1y = 0.780 and to (5.294) > tt (1.734)); 2) there is a positive correlation between self-efficacy and writing skill (rx2y = 0.889 and to (8.251) > tt (1.734)); and 3) there is a positive correlation between vocabulary mastery, self-efficacy simultaneously, and writing skill (R = 0.894 and Fo (33.866) > Ft (3.59)). The results of this research show that vocabulary mastery and self-efficacy contribute to students’ writing skill. Accordingly, vocabulary mastery and self-efficacy can be implemented in the teaching and learning process of writing skill. A teacher needs to provide learning activities which can increase students’ vocabulary mastery and self-efficacy so that students’ writing skill can be influenced positively by those increases.