3.2. Population and Sample
1. Population
The populations in this research was all the second year students at SMP Muhammadiyah 3 Bandar Lampung in academic year 2015-2016.
2. Sample
The researcher selects one class as the sample of the research by using random sampling technique which was using lottery and the result was class
VIIIE as the experimental class.
3.3. Variables
The research consists of the following variables: 1.
Students’ vocabulary achievement is dependent variable Y. It means the achievement of student’s vocabulary partly depends on their ability in
memorizing and understanding a number of English words in language. 2.
STAD technique is independent variable X. It means that STAD will influence the dependent variable in this case is students’ vocabulary
achievement.
3.4. Data Collecting Technique
In order to collect the data, the researcher use the following steps: 1.
Administering pretest The pretest was conducted to know how far the students have mastered the
vocabulary. The number of item in the test was 30 items. The pretest was administered once.
2. Administering posttest
The posttest was conducted to know the students’ improvement of vocabulary after the treatments were given. Similar to the pretest, the researcher used 30
items in the test.
3.5. Research Procedures
1. Determining the sample of the research
The sample of the research was selected by using random sampling technique, which was using lottery. The researcher takes one of six classes of
the second year students at SMP Muhammadiyah 3 Bandar Lampung as the research sample.
2. Selecting instrument material
In this research, there was one pretest that was proper to the grade VIII students of Junior High School. It focused on vocabulary, which is classified
into content words noun, verb and adjective. The materials were taken from student book and teacher-made materials based on School Base Curriculum.
3. Conducting the try out
This test was aimed at finding out the quality of the test which would be used as the instrument of the research, and determined which item should be
revised for the pretest and posttest. 4.
Conducting the pretest It has been conducted before the treatment. It was held to measure the ability
of the students before the students get the treatment.
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