At last stage, level of difficulty for each item must be interpreted in the rank scale of difficulty level, as follow:
Table 1 The rank scale of Level of Difficulty
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The item which has P 0.00 is included as difficult one since there are no students who answer it correctly. Whereas, the item which has P
1.00 belongs to easy one. It means that all students response the item correctly.
The level of difficulty shows the easiness or difficulty of item test for that group. So, the level of difficulty is influenced by students’
competence. It will be different if the test is given to another group.
b. Discriminating Power
Based on the opinion of J. Stanley Ahmann and Marvin D. Glock, “the discriminating power of a test item is its ability to differentiate
between pupils who have achieved well the upper group and those who have achieved poorly the lower group.”
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Moreover, according to Arthur Hughes, “the higher its discrimination index, the better the item discriminates in this way.
The theoretical maximum discrimination index is 1. An item that does not discriminate at all weak and strong candidates perform
equally well on it has a discrimination index of zero. An item that discriminates in favour of the weaker candidates weaker
93
Asmawi Zainul and Noehi Nasoetion, Penilaian Hasil Belajar, Jakarta: PAU-PPAI, UT, 1993, p. 153.
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Suharsimi Arikunto, Dasar-Dasar Evaluasi ..., p. 210.
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J. Stanley Ahmann and Marvin D. Glock, Educating Pupil ..., p. 187.
Interpretation P
Difficult 0.30
Moderate 0.30
– 0.70 Easy
0.70
candidates perform better than stronger candidates has a negative discrimination index.”
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The maximum size of index is +1.00 and the minimum one is -1.00. Negative index means that the item has bad discriminating
power. Whereas, positive one means that it can discriminate well as the desire of test maker. The larger positive value is the better.
The reason for identifying these two groups is that discriminating power allows teacher to contrast the performance of the upper group
students on the test with that of the lower group students. To do this, teacher or test maker can compare the number of students in the upper
and lower group who answered the item correctly. For example, 7 students in the upper group and 3 students in the lower group selected
the correct answer. This indicates positive discrimination since the item can differentiate between these two groups.
To analyze the index of discriminating power of an item, Wilmar Tinambunan states the formula as follows:
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In which: D
: The index of item discriminating power U
: The number of pupils in the upper group who answered the item correctly
L : The number of pupils in the lower group who answered the
item correctly N
: Number of pupils in each of the groups
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Arthur Hughes, Testing for Language ..., p. 226.
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Wilmar Tinambunan, Evaluation of Students ..., p. 139.
U – L
D = N
To sum up, discriminating power indicates the degree to which an item separates the students performed well upper group from those
who performed poorly lower group. In other words, the item that has good discriminating power always presents the fact that students in
upper group answered it correctly more frequently than students in lower group.
c. The Effectiveness of Distractor
The last concentration of item analysis activity is the effectiveness of distractor. It is a procedure specifically related to the multiple-
choice item. Distractors function to divert students from the correct answer if they do not know which is correct.
However, “some distractors, in fact, might not be distracting at all, and therefore
serve no purpose.”
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So, it is important to evaluate the quality of each distractor in multiple-
choice test. In addition, “the primary goal of distractor efficiency analysis is to examine the degree
to which the distractors are attracting students who do not know the correct answer.”
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A good distractor will attract more students from the lower group than the upper group.
The formula for discrimination index can be used in calculating an index of effectiveness for each distractor. The negative value of
distractor means that this distractor has functioned well. In conclusion, the effectiveness of distractor analysis provides the
information about how successful a distractor has diverted students who have not studied well from the correct answer.
E. The Importance of Item Analysis
For the test maker, such as classroom teacher, should know about item analysis in order to know whether the test has performed well to obtain the
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Kathleen M. Bailey, Learning about Language ..., p. 134.
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James Dean Brown, Testing in Language ..., p. 71.
good data as information about students’ performance. Also, it can help make improvement for the next test.
Anthony J. Nitko explains several important uses of item analysis stated below:
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1. Determining whether an item functions as teacher intends
Teacher can know which items function properly by analyzing them through difficulty level and discriminating power activity. A good item
must be in moderate level and differentiate the upper group from the lower group well.
2. Feedback to students’ performance and as a basis for class discussion
In this issue, students’ errors can be corrected and they can know how their performance on each item is marked. Also, the items that are felt
difficult for most of them can be discussed in the class. 3.
Feedback to the teacher about pupil’s difficulties It means that item analysis may provide teacher with the points of
teaching that needs reinforcement and remediation. So, she can focus the instruction on both the group and the individual more efficiently.
4. Area for curriculum improvement
If the certain items which cover a particular point of material are difficult for students continuously or certain kinds of errors occur often, it
may not be test maker’s fault. A more extensive revision of curriculum may be needed.
5. Revising the items
Information abo ut students’ responses to item can be used to revise it.
The good items can be reused for future testing, the rests which are not good need revision.
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Anthony J. Nitko, Educational Test ..., p. 284-286.
