27
3.7 Procedure of Analyzing Data
3.7.1 Validity of the Test
I used content validity I wanted to measure the students’ reading comprehension ability. In line with the issue, Moore 1983:212 asserts that
content validity is most useful with intelligence, ability, achievement and skill, and proficiency test.
Ary 2004:296 as quoted by Furchan states that the researcher should compose the test, which is used as an instrument in the research, by consulting to
the experts in order for the test or the instrument to be valid. I took the following considerations before constructing the items of reading
comprehension test. 1.
Consulting the GBPP Basic Course Outline in selecting the items to be tested in the research. The test items involved the materials of reading
comprehension related to those mentioned in the Basic Course Outline. 2.
Consulting the first and second adviser before constructing the test items. 3.
Choosing the appropriate topics of the passages based on the curriculum used in order for the instrument to cover all the reading material items taught in the
third-grade of junior high schools. Besides using content validity, I used empirical validity by administering
try-out in my research. To find out the validity, I used this formula:
{ }
{ }
2 2
2 2
.
∑ ∑
∑ ∑
∑ ∑
∑
− −
− =
y y
N x
x N
y x
xy N
r
xy
Arikunto, 2002:
146
28
in which: r
xy
= correlation coefficient N = number of students
x = total of item score y = total of the score
3.7.2 Reliability of the Test
Heaton 1984:155 says that reliability is also an essential characteristic of a good test. Meanwhile, Gay and Dielhi as quoted by Sigit 2003:146 define that
reliability is the ability to measure without any mistakes and the result will always be consistence although the test is used by other people in different places. Gay
and Dielhi say that reliability means consistency, dependability and trustworthiness.
Reliability has to do with the result. It means that the examinee will always find approximately the same result if the same test is given to the same examinee
in different occasions, different places and if the answer sheets are graded by different people.
Reliability can be measured by using K-R 21 formula as folows:
⎟ ⎠
⎞ ⎜
⎝ ⎛ −
⎟ ⎠
⎞ ⎜
⎝ ⎛
= kVt
M -
k M
1 1
- k
k r
11
Arikunto, 2002:164
in which:
29
n Y
M n
n Y
Y V
2 2
t
Σ =
Σ −
Σ =
in which: r
11
: instrument reliability k
: total item to be tested M
: total score average Vt
: total varians Y
: total score n
: number of students
3.7.3 Level of Difficulty
Kategori