Abstract :
The Effectiveness of JOOX Application in Improving Students? Vocabulary Mastery Vika Karina Octavia 19113038 Vocabulary is one of the important language components in learning English. Without a proportional amount of vocabulary, anyone will have difficulty in speaking, reading, listening and writing. This research was conducted to answer the research problem whether there was a significant influence on the use of the JOOX application in increasing students' vocabulary mastery. Therefore, it is intended to obtain reliable information whether there is a significant difference in students' vocabulary mastery between the experimental class and the control class. The research design was a quasi-experimental. By using purposive sampling, samples were taken from students of class X IPA 2 and X IPA 5 of SMA Swadhipa Natar. The experimental class was taught using the JOOX application while the control class was taught without using the JOOX application. Before being given treatment, both classes were given a pre-test to find out the extent of students' abilities. After that, both groups were given a post test. In collecting data, the test is used as the main instrument. The test was in the form of multiple choice consisting of 30 questions. The average final scores obtained from both classes were analyzed using the t-test with a significance level of a = 0.05. The significance value (2-tailed) is 0.000