P : Percentage of students’ improvement
y : Pre-test result y1 : Post-test 1
P : Percentage of students’ improvement
y : Pre-test result y2 : Post-test 2
I. Validity of Data
The writer uses validity of the tests to ensure that the research can be acceptable. In analyzing the data, the writer makes the trustworthiness of study
which consists of discriminating power and item difficulty.
8
First, the writer analyzes discriminating power by dividing students into two groups. Those are
upper group and lower group. Second, because there are forty students in the class, she only chooses ten students from the upper group and lower group to
know the discriminating power. Then, she analyzes the students’ answer on pretest, posttest 1, and posttest 2. From the result, she knows whether good or bad
of discrimination power. Next, she analyzes item difficulty to know how many students select the correct answer. From the result, she knows whether high or low
of difficulty item. Finally, she can get the validity by matching the result of discriminating power and difficulty item.
8
See appendix, p. 95.
y1 - y P =
─── X 100 y
y2 - y P =
─── X 100 y
J. Trustworthiness of the Study
The writer uses the trustworthiness of study to analyze the test items. There are two phases:
1. Discriminating Power
The writer uses discriminating power to differentiate students who
have high achievement those who got the score pass KKM and low achievement those who got the score do not pass KKM in answering the
questions. All students are divided into two groups; there are upper group students with high achievement and lower group students with low
achievement.
9
The formula as following:
10
D : The index of discriminating power
B
A
: The number of pupils in the upper group who answered the item correctly
B
B
: The number of pupils in the lower group who answered the item correctly
J
A
: The number of pupils in the upper group J
B
: The number of pupils in the lower group P
A
= B
A
: Proportion the number of pupils in the upper group who J
A
answered the item correctly P
B
= B
B
: Proportion the number of pupils in the lower group who J
B
answered the item correctly
9
Suharsimi Arikunto, Dasar-dasar Evaluasi Pendidikan Edisi Revisi, Jakarta: PT. Bumi Aksara, 2006, p. 211.
10
Suharsimi Arikunto, Dasar- dasar Evaluasi Pendidikan …………., p. 213-214.
B
A
B
B
D = — - — = P
A
– P
B
J
A
J
B
Next, the classification of discriminating scales uses:
11
2. Item Difficulty
The writer uses item difficulty to know whether the questions are too difficult or too easy. Good questions are the questions which are not
too easy or difficult because the easy questions cannot give stimulus to students in trying to solve the problem and the difficult questions make
students give up and do not have a spirit to try because it is out of their mind.
12
The formula as following:
13
P : Index of difficulty
B : The total number of students who selected the correct answer
JS : The total number of students
11
J. B. Heaton, Classroom Testing, New York: Longman Inc, 1990, p. 174.
12
Suharsimi Arikunto, Dasar-dasar Evaluasi Pendidikan Edisi Revisi, Jakarta: PT. Bumi Aksara, 2006, p. 207
13
Suharsimi Arikunto, Dasar-dasar Evaluasi Pendidikan ……........, p. 208
DP REMARK
0.6 – 1.0
Very Good 0.4
– 0.6 Good
0.1 – 0.3
OK -1
– 0.0 Bad
B
P = —
JS
Next, the classification of difficulty item:
14
ID REMARK
– 0.30 High
0.30 – 0.79
Medium 0.80
– 1.00 Low
K. Criteria of the Action Success
The writer and the teacher discussed to determine the criteria of the action success. This study is regarded successful if 75 numbers of students can pass the
KKM.
15
The KKM in the school is 65 sixty five. If the study passes the criteria, thus it is called successful and CAR would be finished, but if it does not pass the
criteria, it is called not successful and needs improvement to continue to the next cycle.
14
John W. Oller, Language Test at School, London: Longman Group Limited, 1979, p. 247.
15
Syaiful Bahri Djamarah dan Aswan Zain, Strategi Belajar Mengajar, Jakarta: PT Rineka Cipta, 2006 p. 108.
