35
35
3.8.2.1 Difficulty Level
The index of difficulty or the facility value of an item simply shows how easy or difficult the particular item proved in the test. It is calculated by using the
formula:
where: P = the facility value index of difficulty
B = the number of students who answered correctly JS = the total number of the students
Criteria Interval Criteria
0.0 P 0.30
0.30 P 0.70 0.70 P
≤ 1.00 Difficult
Medium Easy
Arikunto as quoted by Sudadi, 2005: p.25
3.8.2.2 Discriminating Power
According to Heaton, the discrimination index of an item indicates the extent to which the item discriminates between testers, separating the more able
testers from the less able Heaton, 1975: 173. It is calculated using the formula:
=
36
36 where:
D = the discrimination index BA = the number of students in upper group who answered the item correctly
JA = the number of students in lower group who answered the item correctly BB = the number of students in upper group
JB = the number of students in lower group
Criteria Interval Criteria
D ≤ 0.20
0.20 D ≤ 0.40
0.40 D ≤ 0.70
0.70 D ≤1.00
Poor Satisfactory
Good Excellent
Arikunto as quoted by Sudadi, 2005: p.25
3.7.2.3 Reliability of the Reliability refers to the stability or the c
The correlation of the variables to show the reliability of the test used this formula:
= x
½½
D = −
37
37 where:
The computation of the correlation of the variables of the reliability of the test is presented in the next chapter.
½½
= N ∑ X Y – ∑ X ∑ Y
{N ∑ X − ∑ X }{ N ∑ Y − ∑ Y }
38
CHAPTER IV DATA ANALYSIS
In this chapter present the analysis of the data. The process of the analysis can be seen in the explanation below.
4.1 Reliability of the Test
Tuckman 1978: 160 states that test reliability means that a test is consistent.
The computation of the correlation of the variables showing the reliability of the test was :
r
2 1
2 1
=
[ ] [
][ ]
[ ] [
]
{ }
[ ] [
]
{ }
2 2
451 5339
40 415
4663 40
451 415
4898 40
− −
−
=
{ }{
}
203401 213560
172225 186520
187165 195920
− −
−
=
{ }{
}
10159 14295
8755
=
847 .
12050 8755
= 0.727 r
11
= 727
. 1
727 .
2 +
x
r
11
=
727 .
1 453
. 1
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