this case, the test items of mid-term test of Junior High School have to meet the criteria of what the test measure.
2.4 Reliability
Reliability deals with the consistency of the result. That is how consistent test scores or other evaluation results are from one measurement to the other. If a
test is reliable, then a students’ score on it when compared to the scores of his classmates, should be similar to his relative score on the other test measuring the
same information. Gronlund 1982:132 claims that reliability refers to the consistency of test scores that is, how consistent they are from one measurement
to another. Reliability measures provide an estimate of how much variation that might expect under different conditions.
Reliability is the consistency of the test. It means how consistence or repeatable the test is. If the test is reliable, it indicates that the first test and the
next test are on the same measure. It means that if a students compare with his classmate in a test, so on the next test with the same field of test the score will not
change if it is compared to his classmate.
2.5 Item Discrimination Power
Item discrimination or discrimination power explains how well the items perform in separating the better students from the poorer ones. If the good
students tend to do well on an item and the poor students badly on the same item, then the item is a good one because it distinguishes the good from the bad
students. This is the statement underlying the index of discrimination. To calculate the discrimination power we can use the following steps:
1 Find the number in the upper group who got the items right.
2 Find the number in the lower group who got the items right.
3 Then subtract the number getting it right in the upper group from the
number getting it right from the lower group. 4
Divide this figure by one half of the total numbers of papers in the upper and lower groups.
D = RU-RL ½ T
D : Discrimination power RU: The number of the students in the upper group who answer the item
correctly. RL: The number of the students in the lower group who answer the item
correctly. ½ T: One half of the total number of the students included in the item
analysis. Gronlund, 1981:259
1.0: All the students in the upper group answer correctly and no one in the lower group does.
.00: Is obtained when an equal number of the students in the upper and lower group answer the item correctly.
- : Obtained when more students in the lower group than the upper group answer correctly.
In calculating the discrimination power, the writer divided the students into three groups; there are upper group, middle group and lower group. From the
calculation, we can classify the discrimination power of the items into satisfactory item, good item, reasonably good, and poor item. The item which got zero index
discrimination or negative discrimination power means that the item is bad. The item with negative value means that the students in the lower group perform better
than the students in the upper group. This item must be revised or discarded.
2.6 Item Difficulty
