Thus, the writer needed to find out the definite value of t in the 5 alpha level of significance and 30 degrees of freedom by using interpolation as the
following: t-table for 30 df = 2.042
60 df = 2.000
t-table for 60 =
2. 2−� 2. 2−2.
=
− −
2. 2−� . 2
= −
−
2.042 – t x -30 = -1 x 0.042
-61.26 + 30 t = -0.042 30 t = -0.042 + 61.26
30 t = 61.218 t = 2.041
Based on the computation, the critical value on the t-table for 31 degrees of freedom and 5 alpha level of significance is 2.041. Because t-value is higher
than t-table 13.60 2.041, it means that there is significant differences in the experimental group after they received treatments using subtitled English songs.
4.3.4 t-Test Statistical Analysis of the Pre-Test of the Experimental and Control Group
First, the writer computed the variance of both groups in the pre-test see Appendix 12 for the experimental group and Appendix 13 for the control group.
After getting the variance of the pre-test of both groups, the following is t- test for pre-test computation.
t =
� −�2 √
� �
+
� �
= 8 − .
√ . + . =
1. √1.
+ 1. 8 =
1. √ . 8
= 1.
1. = 1.
After getting the t-value above, the next step was consulting the gaining of
t-value with the critical value on the t-table. First, the writer determined the
degrees of freedom df. Since the number of subject was 32 in the experimental group and 32 in the control group; then, the degrees of freedom is df = N
x
+ N
y
– 2 = 32 + 32
– 2 = 62. For educational research, the 5 0.05 alpha level of significance is used. Based on the t-table with 5 alpha level of significance and
62 degrees of freedom, there is no definite critical value of t in the table. Thus, the writer needed to find out the definite value of t in the 5 alpha level of
significance and 60 degrees of freedom by using interpolation as the following: t-table for 60 df = 2.000
120 df = 1.980
t-table for 60 =
2. −�
2. − .
=
− 2 − 2
2. −�
. 2 =
−2 −
2.000 – t x -60 = -2 x 0.020
-120 + 60 t = -0.040 60 t = -0.040 + 120
60 t = 119.960 t = 1.999
Based on the computation, the critical value on the t-table for 62 degrees of freedom and 5 alpha level of significance is 1.999. Because t-value is lower
than t-table 1.030 1.999, it can be concluded that there is no significant difference between the experimental group and the control group in the pre-test. It
means that there is no difference between the experimental group and the control group on vocabulary mastery before they received the treatment. In other words,
both of the groups had the same characteristics on vocabulary mastery.
4.3.5 t-Test Statistical Analysis of the Posttest of the Experimental and Control Group
