2. Post test The posttest conducted after the students got treatments. The researcher used
the objective test in form of multiple choices for posttest. The time allocation of this test was 90 minutes.
3.5 Instrument of the Research
The research instrument is vocabulary test in the form of objective test, multiple choice. In this research, the researcher administered three kinds of the test; try out
test, pre-test, and post-test. The total number of the items of the try out is 50 items, and the total number of
the items for pretest and posttest was determined from the result of the try out test. In the three of the test contained content words, consist of nouns, verbs, adverbs,
and adjectives. The content of try out test was presented in the table specification below:
Table 1. Table of Specification of Try Out Test
Table of specification of try out test
No. Content
Words Number
of Items
Percentage Item Numbers
1 Noun
13 26
10, 12, 14, 16, 17, 20, 21, 22, 28, 29, 43, 45, 50
2 Verb
13 26
1, 2, 3, 4, 5, 11, 33, 35, 36, 42, 46, 47, 48
3 Adverb
12 24
6, 7, 15, 18, 19, 23, 27, 30, 31, 32, 34, 41
4 Adjective
12 24
8, 9, 13, 24, 25, 26, 37, 38, 39, 40, 44, 49
Total 50
100
3.6 Instrument of the Try Out
In this research, try out is an important thing. It measures the students’ mastery of vocabulary before the students got pretest and posttest. The researcher conducted
try out test in try out class that was VII B. The number of the students in this class
was 40 students consisting 26 females and 14 males. The try out test can be said have a good quality if it has a good validity, reliability,
level of difficulty, and discrimination power.
3.6.1 Validity of The Test
The validity of a test is the extent to which it measures what it is supposed to measure and nothing else Heaton, 1975: 159. Every test, whether it be a
short, informal classroom test or public examination, should be as valid as constructor can make it. The test must aim to provide a true measure of the
particular skill which it is intended to measure Heaton, 1975: 159. There are four kinds of validity, but in this research, the researcher used two of them,
content validity and construct validity.
3.6.1.1 Content validity
Content validity is concerned with whether the test is sufficiently representative and comprehensive for the test. The test should be so
constructed as to contain a representative sample of the course Heaton, 1975: 160. Researcher used the vocabulary that is supposed to be
comprehended by first grade students of Junior High school. The
