The study was aimed at investigating the difference of English vocabulary mastery by the students graduated from Public School and Islamic Boarding School at the English education program of STAIN Palangkaraya. It is because they have different vocabulary learning method in their previous school.
The study used quantitative comparative approach with Ex-post Facto design in finding out the answer of problem of the study. The population of the study consisted of four classes of the second semester students at English Education Study Program of STAIN Palangka Raya. The total number of students was 91 students, who were graduated from Public School, Islamic School, Vocational School and Islamic Boarding School. The writer chose the students graduated from Public School that consists of 39 students and the students graduated from Islamic Boarding School that consists of 5 students as the sample. The sample was determined by using purposive sampling technique. Both of samples were given a test to gain the students’ score in English vocabulary mastery. After getting the data of test score, the writer analyzed the data using t-test pooled variance formula to test the hypothesis. It was found that the result of tobserved was -0,56 and the ttable was 2,02 at 5% of significance level with the degree of freedom (df) was 42. It showed that tobserved was lower than ttable. In addition, the calculation result using SPSS 19 also supported the interpretation of t-test result from manual calculation. The result using SPSS 19 program calculation showed that tobserved was -0,584. It was also lower than ttable at 5% level of significance (2,02). It means that there is no difference of English vocabulary mastery between the students graduated from Public School and those from Islamic boarding school.
The result of testing hypothesis determined that the alternative hypothesis (Ha) stated that there is significant difference of English vocabulary mastery between the students graduated from public school and Islamic boarding school at the English Education Study Program of STAIN Palangkaraya was rejected and the null hypothesis (Ho) stated that there is no significant difference in the English vocabulary between the students graduated from public school and Islamic boarding school at the English Education Program of STAIN Palangkaraya was accepted. In conclude, there is no significant difference of English vocabulary mastery between the students graduated from public school and Islamic boarding school at the English Education Study Program of STAIN Palangkaraya.