D. Technique of Collecting the Data
The data were collected from test instruments. There were two tests that have been employed, the pre-test and post-test. The pre-test was given at the
beginning of the lesson. It was aimed to ascertain the student’s ability in the
material of the simple past tense that is given to the students. The post-test was given the end of the lesson, to know whether or not there was a change on
students’ understanding of the simple past, following of learning by using the STAD and they were not using the STAD. In collecting a require data, multiple
choice test was used. There were 25 items of multiple choices. Both experiment and control group were given the same test.
E. Internal Validity Control
The instrument of this research was a test. Before the instrument was used to the students as the sample of the research, it has been tested to the eight grade
students of MTs Nur Asy-Sy afi’iyah YASPINA, Rempoa. This step was needed
to see the validity of the instrument before it was applied to the sample of the research. Class VIII.B was chosen and it consisted of 30 students, but there were 3
students who were absent and 2 were sick. So, totally there were about 25 students who did the validity test. The instrument was used for pretest and posttest.
The researcher analyzed the instrument by using the formula of the item analysis in test to see the validity of the instrument. The validity of the test could
be seen from the Index of Difficulty ID and Discriminating Power DP from each answer of the questions. The result showed that there were 10 items of the
test were in level of mediocre, 6 items were excellent, 5 items were good, 3 items were worst and 1 item was poor. In order to make it easier to calculate, the items
which in level of mediocre, worst and poor, were eliminated and also changed. So, totally there were about 25 items of multiple choices that were used as the pretest
and posttest in this research.
F. Technique of Analyzing the Data
Analyzing the data is the process to know the result of both experiment and control class and also their differences. The t-
test
formula was used to analyze the difference score of students’ achievement in teaching the simple past with
STAD and without using it. According to Anas Sudijono, this kind of test is used to see whether there is a difference among the two variables which is compared
significantly or the differences only happen by chance. So, the formula and statistical hypothesis are as follow:
t
o
= M
1
= Mean variable of experiment class M
2
= Mean variable of control class SD = Standard of Deviation
SE = Standard Error
Prior to the calculation of t
test
there are several tests to be taken as follows: a. Determining mean of variable X, with formula:
M
1
= M ʹ + i
ʹ
b. Determining mean of variable Y, with formula: M
2
= M ʹ + i
ʹ
c. Determining Standard of Deviation score of Variable X, with formula: SD
1
= i √
∑ ʹ ∑ ʹ
d. Determining Standard of Deviation score of Variable Y, with formula: SD
2
= i √
∑ ʹ ∑ ʹ
e. Determining Standard Error Mean of Variable X, with formula: SE
M
1
=
√
f. Determining Standard Error Mean of Variable Y, with formula: SE
M
2
=
√
g. Determining Standard Error of Different Mean of Variable X and Mean of Variable Y, with formula:
SE
M
1
– M
2
= √
h. Determining t
o
, with formula: t
o
= i. Determining Degrees of freedom df, with formula:
df = N
1
+ N
2
– 2 j. Comparing t
table
with t
o
G. Statistical Hypothesis
The statistical hypothesis of this research can be seen as the following: H
a
: There is significant difference in using STAD towards students’
understanding of the simple past tense. H
o
: There is no significant difference in using STAD towards students’
understanding of the simple past tense. H
a
:
µ
1
=
µ
2
H
o
:
µ
1
≠
µ
2
Then, the criteria used as follows: 1. If t
o
t-test t
t
t-table in significant degree of 0.01 and 0.05, the null hypothesis H
o
is rejected. It means that using STAD technique is effective towards students’ understanding of the simple past tense.
2. If t
o
t-test t
t
t-table in significant degree of 0.01 and 0.05, the null hypothesis H
o
is accepted and the alternative hypothesis H
a
is rejected. It means that the using of STAD
is effective towards students’ understanding of the simple past tense.
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