This research was aimed to investigate the effect of using mobile dictionary on students’ vocabulary mastery and the significant difference on vocabulary mastery in the group: the ones were taught using mobile dicctionary and those who were taught without using mobile dictionary.
The design of this study was explanatory mixed method design which the combination of pre-experimental study and case study. The population of this study was the tenth grade student in SMK IT Subulussalam Samarinda in academic year 2016/2017. The number of the subjects was 37 students. The data were obtained by administering vocabulary test to the students. The research was started by giving pre-test, treatments, and post-test. The data of the test were analyzed by using t-test formula to know the difference of the students’ vocabulary mastery before and after using mobile dictionary. The data from interview were analyzed by using interactive model of data analysis which include data reduction, coding, and conclusion.
In the pre-test, the average score of the students was 68.91. The average score of post-testwas 84.79. The result of the t-test was 6.55 and t-table was 2.028. It means that t-value is higher than t-table (6.55 >2.028). The calculation revealed that the hypothesis about a significant difference between the using of Mobile Dictionary and student’s vocabulary mastery was accepted. All of the students showed that mobile dictionary is helpful for them in vocabulary mastery. They can find out the meaning of the words quickly, easy to remember the word and improve their vocabulary.