2. Sample
Sample of this research are class VII A and VII D. The writer used VII A as a controlled class and VII D as an experimental class. There are 33
students of VII A and 32 students of VII D. During the research, 2 students from VII A were sick and 1 student from VII D was absent. Therefore, there
were 31 students in each class.
D. Technique of Data Collecting
The writer took pre-test and post-test in this research. The pre-test was conducted to know that the students in both classes have the homogenous skill
in English and to know their earlier knowledge of vocabulary before the treatment. After the treatment finish, the writer gave post-test to both classes
and compared their vocabulary achievement. Before the test was given for pre-test, the writer did the validity of test to
seventh grade of MTs N 13 Jakarta class VII C based on the random. The chosen class as controlled and experiment class is based on the purposing
sampling. Then, the writer examined the validity, reliability, index of difficulty, and discriminating power using ANATES software.
In this research, both class experiment and controlled class were given two test about vocabulary based on their source books: Pre-test and Post-test
1. Pre-test There are 40 items of multiple choices. The score per item is 2.5 for correct
answer. Students will get 100 point if they can answer all the questions correctly. The same test was given for both classes. The purposes of pre-test
are to know the homogenous skill in English of the students and to know their earlier knowledge of vocabulary before the treatment.
2. Post-Test As same as the pre-test, there are 40 items of multiple choices. The score per
item is 2.5 for correct answer. Students will get 100 point if they can answer all the questions correctly. The purpose of post-test is to know the
improvement of students in their vocabulary achievement after the treatment.
E. Technique of Data Analysis
The technique of data analysis will use the t-test formula that is adapted from Suharsimi Arikunto.
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The t-test is used to compare the score in pre-test and posttest. After getting the score from pre-test and post-test, the writer
analyzes it by using statistic calculation of T-Test formula with the degree of significance 5.
The t-test formula can be formulated as follow:
t
=
= Mean of the Gained Score of Experiment Class = Mean of the Gained Score of Controlled Class
= Standard Deviation of Experiment Class = Standard Deviation of Controlled Class
= Number of students in Experiment Class = Number of students in Controlled Class
In order to get the calculation of T-test, there are several steps to be taken:
The following steps describe as follows:
1. Determining mean of gained score of experiment class:
=
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Suharsimi Arikunto, Prosedur Penelitian Suatu Pendekatan Praktik, Sixth edition, Jakarta: Asdi Mahasatya, 2006, p. 311
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