From the distribution above, it can be concluded that the first try out instrument had 27 valid items and 8 invalid items. The computation of validity
can be seen in appendix 5. b The following is the example of counting the validity of item number 2 of the
second try out:
The value of
xy
r
is
:
xy
r
= 0.394
The item number 2 of the try out test was valid since its r
xy
= 0.394 higher than critical value 0.349.
After all the item numbers were analyzed, there were 25 valid items from 35 items and the rest were invalid. They were presented in the following table:
Table 4.2 The Validity of the second Try-out Test
Criteria Number of Items
The Total Number Valid
2, 3, 5, 6, 8, 10, 12, 13, 14, 15, 16, 18, 20, 21, 22, 23, 24, 26, 28,
29, 31, 32, 33, 34, 35 25
Invalid 1, 4, 7, 9, 11, 17, 19, 25, 27, 30
10
2 2
xy
761 19631
32 27
27 32
761 27
675 32
r
X
From the distribution above, it can be concluded that the second try out instrument had 25 valid items and 10 invalid items. The computation of validity
can be seen in appendix 5.
4.3.2 Reliability of the Test
Reliability of the test shows the stability or consistency of the test scores when the test is used. The following is the computation of the reliability of the
instrument. The formula is:
If r
11
r
table,
so the instrument is reliable Based on the try out table, it can be gotten:
a The computation of the first try out r
11 =
, ,
,
= 1. 042 The result of commutating reliability of the first try out instruments was
1.042. For α = 5 with N = 32, and r table = 0.349. Since the result of r₁₁ was higher than r table, it was concluded that the first try out instrument was reliable
and could be used as the instrument to get the following data. The computation can be seen in appendix 6.
b The computation of the second try out r
11 =
, , ,
= 1. 044
Vt pq
Vt 1
- k
k r
11
The result of commutating reliability of the second try out instruments was 1. 044. For α = 5 with N = 32, and r table = 0.349. Since the result of r₁₁ was
higher than r table, it was concluded that the second try out instrument was reliable and could be used as the instrument to get the following data. The
computation can be seen in appendix 6.
4.3.3 Discriminating power
According to Heaton 1975: 174 the discriminating power measured how well the test items arranged to identify the differences in the students’ competence. After
the trial test was carried out, an analysis was made to find out the discriminating power of each item.
a The computation of discriminating power of the first try out test instruments of item number 2:
Table 4.3 The Computation of Discriminating Power
Upper Group Lower Group
No. Code
Score No.
Code Score
1 2
3 4
5 6
7 8
9 10
11 12
13 14
R-16 R-1
R-14 R-19
R-25 R-32
R-3 R-4
R-7 R-8
R-28 R-30
R-9 R-10
1 1
1 1
1
1
1 1
1 1
1 1
1 1
1 2
3 4
5 6
7 8
9 10
11 12
13 14
R-29 R-2
R-6 R-12
R-24 R-27
R-31 R-20
R-21 R-26
R-13 R-15
R-5 R-11
1 1
1 1
1 1
1 1
1 1
1
