Population Sample Research Participants
32 students. The formula to find the correlation coefficient by the Pearson product
moment and the mean of the vocabulary test score is showed below.
Pearson Product Moment:
= ∑
�
− ̅
�
− ̅
�=1
− =
∑ −
�
= any x value ̅ = mean of x
�
= any y value ̅ = mean of y
= standard deviation of x = standard deviation of y
= number of pairs of x and y = standard score for x
= standard score for y
Mean Score:
̅ =
∑
̅ = mean of m ∑ = sum of m
= number of m Based on Siregar 2013, the correlation between two variables can be known
through the coefficient of correlation. Positive correlation appears if the coefficient is close to +1, while negative correlation appears if the coefficient of correlation is
close to -1. There is no correlation if the coefficient of correlation is 0. There are some ways to measure the correlation between variables. Pearson
product moment was chosen to analyze the data because Pearson product moment
33 can measure the significance of a linear association between two variables which
was derived from the r. According to Siregar 2013, the number of coefficient correlations can show
the significance of the relationship of two variables. Coefficient correlative starting from 0.00 to 0.199 shows a very weak relation. Coefficient correlative starting from
0.20 to 0.399 shows weak relation. Coefficient correlative starting from 0.40 to 0.599 shows an adequate relation, it is not weak nor strong. Coefficient correlative starting
from 0.60 to 0.799 shows strong relation, and 0.80 to 1 shows that two variables has very strong relationship. Below is a table of coefficient correlation r and the
strength of the relationship.
Table 3.1 Coefficient Correlation and the Significance of the Relationship
Coefficient Correlation r Significant Relationship
0.00 – 0.199
Very weak 0.20
– 0.399 Weak
0.40 – 0.599
Adequate 0.60
– 0.799 Strong
0.80 – 1
Very Strong
As cited in Siregar 2013