34, 35, 36, 37, 38, 39, and 40. The invalid numbers were 1, 2, 10, 13, 15, 30, 31, and 33.
4.1.1.2 Reliability
The formula that was used to calculate reliability was K.-R.21
In which, : Reliability
: The number of the instrument items : The mean of the score
t
V
: The variance The test instrument was considered being reliable if the r
xy
r
table
for α = 5 . By using Kuder and Richardson formula, I considered that the transformation
of the try out is reliable. Here was the computation. First, what we have to find is the variance of the test, the symbol was
t
V
. The formula used to find
t
V
was:
In which,
t
V
= the variance N= the number of the students who did the try out
y = the score of the students
2
y
= the square of the students‟ total scores
11
r
k
m
N N
y y
V
t
2 2
42 42
1170 34772
2
t
V
44
Therefore, the test variance was 51.884. The next step, I found the mean of the result of the test. The formula was:
As the result, the mean score of the test instrument for pre test was 27.86. The last step, I tried to find the reliability of the test by using K
–R21 formula as follows:
For α = 5 and the number of the students were 42, the r
table
= 0.304. Since r
xy
r
table,
0.8580.304 the try out test was reliable.
4.1.1.3 Difficulty Level
884 .
51
t
V
N y
m
42 1170
m
86 .
27
m
88 .
51 40
86 .
27 40
86 ,
27 1
39 40
11
r
858 .
11
r
45
The formula that was used to count the difficulty level of each item was:
In which, P = the facility value index of difficulty
B = the number of the students who answered correctly Js = the total number of the students
For instance, item number 1 of test instrument A for pre test, there were 29 students who answered correctly. Therefore, the computation is as the
following:
Table 4.2 The calculation of Difficulty Level
Upper group Lower group
No Code
Score No
Code Score
1 T-018
1 22
T-015 1
2 T-011
1 23
T-027 3
T-012 1
24 T-008
1 4
T-019 1
25 T-041
5 T-037
1 26
T-032 6
T-021 1
27 T-038
1 7
T-039 1
28 T-029
1 8
T-013 1
29 T-010
1 9
T-024 1
30 T-031
1 10
T-023 1
31 T-009
1 11
T-036 1
32 T-002
12 T-003
1 33
T-020 13
T-017 1
34 T-028
1 14
T-006 35
T-035 15
T-004 1
36 T-033
16 T-022
1 37
T-040 1
17 T-001
1 38
T-005 1
18 T-034
1 39
T-026 19
T-007 1
40 T-016
20 T-030
41 T-025
JS B
P
46
21 T-014
1 42
T-042 19
10
B = 19+10 = 29 Js = 42
According to the criteria, the item number 1 was medium. For the other items, I used the same formula. It could be seen on the appendix 5
4.1.1.4 Discriminating Power
Kategori