test, after that multiply with 100.
19
The formulation of difficulty index is shown below:
Where: ID: index difficulty
: the number of pupils who answered the item correctly in the upper group
: the number of pupils who answered the item correctly in the lower group
N: the number of pupils who took the test
20
Table 2.1 The classification of Index Difficulty:
21
Difficulty Level 0.00 - 0.30
Difficult 0.30 - 0.70
Medium 0.70 - 1.00
Easy
The test is appropriate for being tested if each item in the examination passed by half of the students.
22
Difficulty Index is relevant for determining whether students have learned the idea of
being tested. It also plays an important role to determine the ability to discriminate the students who know the concept of materials being
tested and those who do not.
b. Discrimination Index
Discrimination index refers to the ability of an item to distinguish among the students on the basis of how well they know the material
19
Arikunto, p. 208.
20
Ibid.
21
Ibid., p. 210.
22
Louis J. Karmel, Measurement and Evaluation in the Schools, London: The Macmillan Company, 1978, p. 381.
that has been tested. It is also important to note that the difficulties of items can identify the comprehension ability among the students. As
well as item difficulty, the student will also differ into two groups; upper and lower group. All of the groups will be a representative for
27 from the whole student who took the test. The higher the percentage of discrimination index means the
ability of items to differentiate the comprehension ability among students is high.
23
The discrimination index is range between -1 to +1. An item with positive discrimination is the one that is more frequently
answered correctly by students who scored high on the test as a whole than by students who scored low.
24
Also, Surhasimi stated that a good test item is the one having discrimination index between 0.4 until 0.7.
25
Discrimination index can be obtained by subtracting the number of students in a lower group who get the item right L with the number
of students in the upper group who get the item right U. After that the result will divide with the half total number of student both in lower
and upper group. The formulation of discrimination index as shown below:
Where: DI = discrimination index
: the number of pupils who answered the item correctly in the upper group
: the number of pupils who answered the item correctly in the lower group
: the number of pupil in the upper group the number of pupil in the lower group
23
Arifin, op. cit., p. 273.
24
Airasian, op. cit., p. 388
25
Arikunto, op. cit., p. 218.
: the proportion of pupil who answered the item correctly in the upper group
: the proportion of pupil who answered the item correctly in the lower group
26
Table 2.2 The classification of Discrimination Index:
27
DP Quality
Recommendation 1.0 - 0.70
Excellent Retain
0.70 - 0.40 Good
Possibilities for improvement 0.40 - 0.20
Mediocre Need to checkreview
0.00 - 0.20 Poor
DiscardReview in Depth -0.01
Worst Definitely Discard
A test has discrimination index if more of the upper group answer the questions correctly than the lower do.
28
By Analyzing the discrimination index of each item, it will show the information that
helps the teacher in identifying the flaws, giving further explanation about material, and also giving the feedback in learning materials.
c. Distracter Effectiveness
To diagnose the problem shown in difficulty and discrimination index, the proportion of student choosing the distracter can also be
calculated to assess how the distracters are functioning. It can be compared with the proportion of students choosing the correct
response. The distracter is considered as effective if it is chosen by the most of students in a lower group. If the distractor is mostly chosen by
26
Ibid, pp. 213-214.
27
Ibid, p. 218.
28
Karmel, op. cit.
