33
her as the researcher to totalizing it into the final score. This score would be students’ scores for their writing skill and it would help the researcher classifying
students’ writing proficiency.
3.6 Try Out
Before doing the test, it was tried out then analyzed. Try out test conducted on March 2009. Try out was necessary since the result was used to make sure that
the measuring instrument had such characters like validity and reliability. It was also used to measure the difficulty level of the essay test itself. It was used to
prove whether the instrument was good or not. In this study, the writer did the try out to another class VIIID of the eighth
grade of SMP N 2 Mayong Jepara. In this class, there were actually 33 students but here the writer only put 15 students. Then the rest of the students were taught
by their teacher as usual. It was done to save the researcher’s time in collecting and analyzing the data. Although, there were only fifteen students, but they could
be the representative of the other students especially the eighth graders of SMP N 2 Mayong to describe a descriptive text based on the hand puppets in the teaching
and learning writing English. The try out test consisted of four items. They were the scoring of writing
contain, rhetoric’s step, language, spelling. There were 15 respondents and they had to do the test in a limited time. The data obtained through the rating scale
were analyzed quantitatively.
34
1 Validity
Concerning with validity, Heaton 1979: 152 proposes that the validity of a test is the extent to which it measures what it supposed to
measure. Every test, he continues, whether it is a short, informal classroom test or a public examination, should be as valid as the constructor make it. The
test must aim to provide a true measure of the particular skill which it is intended to measure. A test is valid if it coincides with its purposes.
The result is consulted to critical value for r-product moment. If the obtained coefficient is higher than the critical value for r-product moment, it
means that a paragraphs is valid at 5 alpha level of significance. To calculate the validity of a test, I used this formula:
r
xy =
{ }{
}
∑ ∑
∑ ∑
∑ ∑ ∑
− −
−
2 2
2 2
y Ny
x x
N Y
X XY
N
in which: r
xy
: the correlation of the scores on the two halves of the test N : the number of the students
∑X : the students total score from each item ∑Y : the students total score from all items
∑X
2
: the sum of quadrate from each item ∑Y
2
: the sum of quadrate from all items ∑XY : the sum of the multiple of the score from each item and all items
35
In try out instrument, there was descriptive text writing. In this writing, there were four items that would be analyzed; content, rhetoric’s step,
language, and spelling.
2 Reliability
Reliability is necessary characteristics of any good test: for it to be valid at all, a test must first be reliable as measuring instrument Heaton 1975:
154. If the test is administered to the some candidates on different occasions with no language practice work talking place between this occasions, then,
to the extent that it produces different results, it is not reliable. Reliability measured in this way is commonly referred to as test
reliability. In short, in order to be reliable, a test must be consistent in its measurements. There are number of ways in estimating test reliability. In this
study, the reliability of the test was measured by comparing the obtained value with r-value product moment. That is, if they obtained value is higher
than the table r-value, the test can be said reliable. To calculate the reliability of the test, I used the formula:
r
11
= 2xr ½ ½ 1
+ r ½ ½ In which:
r
11
= reliability of instrument r
1212
= r
xy
namely reliability obtained by correlating half of the test with the other half.
36
Before applying the formula above, we should find out r
xy
first. The step to get r
xy
was: r
xy =
{ }{
}
∑ ∑
∑ ∑
∑ ∑ ∑
− −
−
2 2
2 2
y Ny
x x
N Y
X XY
N
in which: r
xy
: the correlation of the scores on the two halves of the test N : the number of the students
∑X : the students’ total score of odd items ∑Y : the students’ total score of even items
∑X
2
: the sum of quadrate of odd items ∑Y
2
: the sum of quadrate of even items ∑XY : the sum of the multiple of odd score and even score
3.7 Method of Data Analysis
