spelling. Consequently, it determines the computation of validity, reliability, difficulty level, and the discriminating power of each item. Here, for the benefit of
the computation, the five components were considered the five items of the writing test. So, there were five items altogether. The formula used to estimate the
validity of the writing test was the same as that used for the past tense test, i.e. Pearson Product Moment formula.
Finishing testing the validity of each item, the writer found that all the five items or the five criteria of writing scoring were valid.
3.6 Reliability of the Test
A test is reliable to the extent that it is consistent with itself, that is, it ranks the individuals in essentially the same position on its successive application. In other
words, if a measuring device is tested on the same subjects on two different occasions, for example, the result will more or less be similar. Thus, reliability is a
characteristic that a measuring device must possess in the sense that its reliability will influence the reliability of the research result.
Since there are two tests used in this study, i.e., objective type test for the past tense test and essay type for the writing test, two different formulas will be
applied. To calculate the reliability of the Past Tense test, the following Spearman-Brown Formula was used:
r
11
= 1
2
2 21
1 2
21 1
r r
+ ;
with r
1212
=
∑ ∑
∑ ∑
∑ ∑ ∑
− −
− }
}{ {
2 2
2 2
Y Y
N X
X N
Y X
XY N
in which: r
11 :
reliability of the instrument r
1212 :
Pearson correlation of odd and even value. Based on the formula, the writer found out the value of r
1212
=0.718 and the value of r
11
=0.836. After finding the result of r
11
, the writer then consulted it to the r
table
. And for α=0.05 with the number of subject 40, the value of r
table
is 0.312. The instrument is said to be reliable if r
11
r
table
. Thus, with the result of r
11
=0.836, the test is considered reliable.
Meanwhile, to test the reliability of the writing test, the following formula was used:
Where:
r
11
= Reliability
index k
= Number of item
2 t
σ = Total variance
2 b
σ = Item variance To figure out the total variance, the following formula was used:
The item variance was obtained by applying the following formula: ⎟⎟⎠
⎞ ⎜⎜⎝
⎛ ∑ ⎟
⎠ ⎞
⎜ ⎝
⎛ −
=
2 2
11
- 1
1 k
k r
t b
σ σ
N N
Y Y
2 2
2
∑ −
∑ =
t
σ
N N
X X
2 2
2
∑ −
∑ =
b
σ
The instrument is considered reliable if r
11
r
table
. The writer obtained that r
11
= 0.866, which means higher than r
table
, thus, the writing instrument is reliable.
3.7 Item Analysis
Since the validity and reliability of the overall test is indirectly dependent upon the quality of each item, after a test has been administered and scored, it is
desirable to evaluate the effectiveness of each item. This is done by analyzing the students’ responses to each item. This activity is commonly called item analysis.
This analysis gives us information regarding how well each item in the test functioned so that we can discover which items need to be improved, revised, or
discarded. Item analysis covers the calculation of the level of difficulty and the discriminating power of each item.
3.7.1 Difficulty Level
A good test item should not be either too easy or too difficult. An easy test will not stimulate students to figure it out. An excessively difficult one, on the other
hand, will students desperate and will be reluctant to try to solve it. The difficulty level of a test is, therefore, indicated by the percentage of
the students who get the items right. Thus, the more difficult an item is, the fewer will be the students who answer correctly.
To find out the difficulty level of each item in the past tense test, the writer used the following formula:
P = JS
B
in which: P : index of difficulty
B : the number of students who answer the item correctly JS : the total number of students.
Arikunto, 2002:212 By using the formula, the P value of each item can be found. Also, in
order to figure out the difficulty level of each item, the writer referred to the criteria of P value suggested by Arikunto 2002:214. The criteria are presented in
table 3.2.
Table 3.2 The Criteria of Difficulty Level.
Interval Criteria 0.00 P
≤ 0.30 0.30 P
≤ 0.70 0.70 P
≤ 1.00 Difficult
Medium Easy
Taken from Arikunto 2002:218.
After computing the difficulty level of all items and consulting them to the criteria of the difficulty level, the following data was obtained:
Table 3.3 Results of the Difficulty Level of Past Tense Test Items
criteria Numbers of item
Medium 1, 2, 3, 4, 5, 7, 8, 12, 14, 15, 16, 17,
19, 20, 21, 22, 24, 25, 26, 27, 28, 30, 32, 33, 35, 36, 38, 39, 41, 43,
46, 49, 50.
easy 6, 9, 10, 11, 13, 18, 23, 29, 31, 34,
37, 40, 42, 44, 45, 47, 48.
3.7.2 Discriminating Power
Finding out the discriminating power of an item is necessary for revealing how well the item discriminates between high and low scorers on the test. If good
students tend to do well on an item and poor students do badly on the same item, it means that the item is good because it distinguishes the good from the bad
students. The higher the discriminating power of an item is, the better the item discriminates the good students from the poor one.
In terms of discriminating power of a test item, Heaton 1975:173 states: “The discrimination index of an item indicates the extent to which the
item discriminates between testees separating the more able testees from the less able. The index of discrimination tells us whether those students
who performed well on the whole test tended to do well or badly on each item in the test.”
To figure out the discriminating power of each item of the past tense test, the following formula was used:
D =
B B
A A
J B
J B −
D = The discrimination index
B
A
= The number of students in upper group who answered the item correctly B
B
= The number of students in lower group who answered the item correctly J
A
J
B
= The number of students in upper group or in lower group By using the above formula, the discrimination index of each item can be
revealed. After knowing the discrimination index of each item, a table of criteria is then used to classify their category. Arikunto 2002:223 suggests the criteria of
discrimination index in table 3.4.
Table 3.4 The Criteria of Discrimination Index
Interval Criteria 0.00 D 0.20 Poor
0.20 D 0.40 Medium 0.40 D 0.70 Good
0.70 D 1.00 Satisfactory
Taken from Arikunto 2002:201.
Table 3.5 presents the result of the discriminating power analysis of all items.
Table 3.5 Result of the Discriminating Power Analysis
Criteria Item Numbers
Poor 3, 8, 9, 15, 21, 24, 25, 26, 37, 46, 47
Total: 11 Medium 0
Good 28
Satisfactory 1, 2, 4, 5, 6, 7, 10, 11, 12, 13, 14, 16, 17,
18, 19, 20, 22, 23, 27, 29, 30, 31, 32, 33, 34, 35, 36, 38, 39, 40, 41, 42, 43, 44, 45,
48, 49, 50. Total: 38
3.8 Data Collecting
Once the research instrument was prepared, the data collecting was the successive step to conduct. Since the study sought to reveal the students’ achievement in past
tense as well as their ability in writing recount and to prove whether there was a significant correlation between those two variables, past tense test and writing test
were administered to gain the intended data. Therefore, having finished the instruments and analyzed their validity,
reliability and the effectiveness of each item, the writer administered the two tests
to the subjects of the study. The tests were held on Saturday, September 30
th
2006 at 10 o’ clock. The students were required to do each test in 50 minutes.
Once the tests were done, they were then scored. The scores of the test were the data required by this study. After the data were gathered, they were then analyzed
and interpreted.
3.9 Data Analysis
