In which:
1
X
: The mean of upper group
2
X
: The mean of lower group
2 1
: The total quadrate of individual deviation from upper group
2 2
: The total quadrate of individual deviation from lower group n
: 27 x N upper and lower group
Table 2.2 The classifications of the index of Discriminating Power D are:
47
Index of Discriminating Power
Classifications
0.70 – 1.00
Excellent 0.40
– 0.70 Good
0.20 – 0.40
Satisfactory ≤ 0.20
Poor Negative value on D
Very poor
c. The Effectiveness of Distracter
Based on, Mozaffer and Farhan Jaleel’s article that, “another important
technique is analysis of distractors, that provides information regarding the individual distractors and the key of a test item.”
48
It means that, the teacher will know the ability of the students from the answer which they have chosen.
47
Anas Sudijono, Pengantar Evaluasi Pendidikan, Jakarta: PT. Raja Grafindo Persada, 2006 p. 389.
48
Mozaffer Rahim Hingorjo Farhan Jaleel, Analysis of One-Best MCQs: the Difficulty Index, Discrimination Index and Distractor Efficiency,
Karachi: Journal of Pakistan Medical Association, 2012
, p. 1.
Actually, the test item which can be called good quality that is the distractor will be chosen by students who answer incorrect equally. On the contrary, a poor test
item is the distractor will be chosen unequally. Besides that, the test item will be called good quality too if many upper group can answer correctly and only a little
lower group can answer correctly.
3. The Difficulty Level and the Discriminating Power
According to J. Stanley Ahmann and Marvin D. Glock, “It has been long
known that the discriminating power of an item is influenced by its difficulty.”
49
To support, it also tells how difficult or easy the questions were, the difficulty index, and whether the questions were able to discriminate between students who
performed well on the test, from those who did not, the discrimination index.
50
Logically, after analyzing the level of difficulty the teacher will get information that it can be known the level of difficulties of each item whether the test
items are included in easy, moderate, or difficult level. Then, from that level of difficulties the teacher can discriminate the students whether they are included in
upper or lower group. As an example, based on Zainal
Arifin’s statement, the upper group will be able to answer the question rather than the lower group.
51
So, it can be concluded that the difficult level only can be answered by the upper group of students and it cannot
be answered by the lower group of students. So, after analyzing the test items based on the difficulty level it will be better
if the teacher analyzing the discriminating power in the same times and procedures. Because, in analyzing the test items the teacher not only know the level of difficulties
of those items but also know how well the test items discriminate the upper and lower group students.
49
J. Stanley Ahmann and Marvin D. Glock, loc. cit. p. 189.
50
Mozaffer Rahim Hingorjo Farhan Jaleel, loc. cit.
51
Zainal Arifin, op. cit., p. 133.
According to Heaton, “Facility values and the discrimination indices are usually recorded together in tabular form and calculated by similar procedures.”
52
Above all, by analyzing the test items in term difficulty level and discriminating power, the teacher will know the qualities of the test items whether the
test items have an easy, moderate, or difficult level and a high or low discriminating power.
To calculate them, it can use the formula as follows:
53
In which: FV
: The index of difficulty R
: The number of correct answers N
: The number of students taking the test D
: Discriminating index U
: Upper half L
: Lower half n
: Number of candidates in one group
52
J.B Heaton, op. cit., p. 182.
53
Ibid.
FV =
or FV =
D =
