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
researcher arranged the instrument related to which is content words because content words can cover the material. The material is
vocabulary of occupation, contain: noun, verb, adjective, and adverb. The content of pre test and post test were presented in the table
specification below:
Table 2. Table Specification of Pre test Table of specification of pre test
No. Content
Words Number
of Items
Percentage Item Numbers
1 Noun
11 27.5
4, 8, 10, 12, 13, 16, 17, 18, 24, 37, 40
2 Verb
7 17.5
1, 3, 9, 28, 30, 31, 38 3
Adverb 11
27.5 6, 7, 11, 14, 20, 21, 22, 32, 33, 34,
39 4
Adjective 11
27.5 2, 5, 15, 19, 23, 25, 26, 27, 29, 35,
36 Total
40 100
Table 3. Table Specification of Post test Table of specification of pre test
No. Content
Words Number
of Items
Percentage Item Numbers
1 Noun
11 27.5
2, 6, 8, 11, 13, 17, 24, 28, 35, 38, 40
2 Verb
7 17.5
3, 5, 16, 21, 23, 26, 36 3
Adverb 11
27.5 7, 9, 12, 14, 19, 27, 29, 30, 31, 32,
39 4
Adjective 11
27.5 1, 4, 10, 15, 18, 20, 22, 25, 33, 34,
37 Total
40 100
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