P : percentage of stude nts’ improvement
y : post-test 1 y2 : post-test 2
G. The Trustworthiness of Test
To analyze the examined test items, the writer uses the trustworthiness of test. There are some ways including:
1. Test Validity Validity is the component criteria for evaluating the test or as a
measure of the test. It could be about the representation of test toward the material that is being given for the students. Milton added that validity
addresses whether a test measures what it is supposed to measure and not something else.
9
Before administering the pre-test, the writer analyzes the validity and the reliability of pre-test instrument in order to find out
whether the test is valid or good to be used. According to Arikunto, information will be valid if appropriate with the fact and the test will be
valid if it can be measure what it should be measure
10
Before administering the test, the writer used auditing by asking the advisor to review and evaluate the study to ensure the validity of the
instruments.
11
Then, after the students did the pre-test, she used the Anates software developed by Drs. KARNO To, M.Pd and Yudi Wibisono, ST to
calculate the instruments ’ validity and reliability scores.
Table 3.1 The criterion of
“koefisien korelasi”
12
Scale Remark
0.80 – 1.0
Very high
9
James Milton, Measuring Second Language Vocabulary Acquisition, British Library, 2009, p. 18.
10
Prof. Dr. Suharsimi Arikunto, Dasar-dasar Evaluasi Pendidik an,Jakarta: Bumi Aksara, 2010, pp. 58
– 59.
11
Creswell, op.cit., p. 259.
12
Prof. Dr. Suharsimi Arikunto. op.cit., p. 75.
0.60 – 0.80
High 0.40
– 0.60 Enough
0.20 – 0.40
Low 0.0
– 0.20 Very low
After the calculation using “ANATEST”, the validity value or XY
correlation of the pre-test instrument used in this study was 0.69. It means the test is valid and categorized into high quality. It was gotten the data
from 40 forty questions multiple choices that was examined before and got 25 twenty- five questions that was valid through ANATES software.
Instrument that was valid are number 1, 4, 5, 7, 9, 10, 13, 16, 17, 18, 20, 21, 22, 23 24, 26, 28, 29, 31, 33, 34, 37, 38, 39, and 40. Meanwhile, the
reliability of the instrument was 0.81 which means the test is valid and categorized into very high reliability. Then, the validity value of post-test
2 used in this study was 0.55. it means the test is valid and categorized into enough quality. Then, the reliability of the instrument was 0.71 which
means the test is valid and categorized into high reliability. 2. Discrimination Power
The analysis of discrimination power test items is to know the performance of the test through distinguishing students who have high
achievement and low achievement. Item discrimination provides more detailed analysis of the test items difficulty, because it shows how the top
scores and lower scores performed on each item. The formula as following:
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D =
D : The index of discriminating power U : The number of correct answer in the upper group
13
Sugiyono, op.cit. p. 257.
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