R = r
2
x 100 = 0.444
2
x 100 = 0.197 x 100
= 19.7 Note:
R = value of determinant coefficient
r
2
= value of the squared correlation coefficient So, b
ased on the result of determination coefficient, students’ vocabulary mastery contributes to students’ writing achievement as much 19.7.
3. Test of Hypothesis
To test the hypotheses, the correlation coefficient from the calculation r
xy
is compared to correlation coefficient from Product Moment table r
t
. In the term of the statistical hypotheses, these can be portrayed as follows:
1. If r
o
r
t
= H
a
is accepted. There is a relationship between vocabulary mastery and writing achievement.
2. If r
o
r
t
= H
a
is rejected. There is a no relationship between vocabulary mastery and writing achievement.
To find r
xy
or r
o
, the degree of freedom must be determined with the formula: d
f
= N –nr
= 44 – 2
= 42 Note:
d
f
= degree of freedom n = number of cases respondents
nr = number of variables In the table of significance see appendix 10, it is shown that the r
t
of a two tailed test in the significance of 1 and d
f
of 42 is found to be 0.384. Based on the score of r
o
0.444, it is indicated that the score of r
o
is higher than r
t
, in which 0.444
0.384. It means that H
a
is accepted; or in other words there is a relationship between vocabulary mastery and writing achievement.
Moreover, the result of t
count
or to is compared to t
table
in order to find the significance of variables. The formula of getting t
count
is presented as follows: Formula:
t
c
= r √n −
√ − r
2
Description of the formula: t
count
= t
value
r = 0.444 n = 44
Calculation: t
c
= r √n −
√ − r
2
= .
√ − √ − .
2
= .
√ √ − .
= .
. √ .
= .
. √ .
= .
. = . 0
The formulation of test: a. If t
o
t
table
, it means that the null hypothesis is rejected and there is significant relationship between the two variables.
b. If t
o
t
table
, the null hypothesis is accepted and there is no significant relationship between the two variables.
From the table of significance see appendix 11, it is obtained that t
table
of 1 and d
f
= 42 is 2.69807. It indicates that t
o
is higher than t
table
, in which 3.210 2.698. Therefore, the alternative hypothesis H
a
is accepted. In other words, there is a significant relationship between vocabulary mastery and writing achievement.
According to the result of the calculation of Pearson Product Moment above, the value of correlation coefficient r
o
is 0.444. To interpret the gravity of 0.444, the table of “r” product moment shows that the correlation value is in between
0.40 —0.59, or moderate level. The medium correlation means that the
relationship tends to the positive value and there is no negative relationship. The table of “r” interpretation was adopted from Jonathan Sarwono’s theory.
Table 4.9 The Interpretation of Correlation Coefficient
Coefficient Interval Degrees of Correlation
0.00 —0.19
Very weaklow 0.20
—0.39 Weaklow
0.40 —0.59
Mediummoderate
0.60 —0.79
Strong 0.80
—1.00 Very Strong
B. Discussion
Based on the data description of vocabulary mastery, it is found that the seventh semester students of Department of English Education in academic year
20162017 commonly have good vocabulary mastery, which is indicated by the result of the average score found is 74.27 and the mode score is 76.00. However,
although the students are considered to have good vocabulary mastery, there are still some students who have limited knowledge of vocabulary. From the data of
vocabulary mastery score, it is shown that almost a half of the total sample obtained score under the mean score. Therefore, some students of Department of
English Education should learn more about vocabulary.
