P : percentage of students’ improvement y : pre-test result
y2 : post-test 2
J. The Trustworthiness of the Study
In analyzing the test items, there are two ways that will be used to know the trustworthiness of the data, and it is explained as follows:
1. Discriminating Power
A good test item should have a discriminating power. The discriminating power of a test item is an index that shows its ability to
differentiate between pupils who achieved well the upper group and those who have achieved poorly the lower group. It is supported by the theory of
Norman E. Gronlund in his book, Constructing Achievement Test, he stated that “discriminating power is the comparison between the number of students
in the upper group and lower group who answered the item correctly”.
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To find out the discriminating power index, it will be used the following formula:
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D : The index of discriminating power Ru : The number of pupils in the upper group who answered the item correctly
RL : The number of pupils in the lower group who answered the item correctly
5
Norman E. Gronlund, Constructing Achievement Test, New Jersey: Prentince-Hall, Inc, 1982. p.103.
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Norman E. Gronlund, Constructing...
Ru – RL
D = ──── ½ T
½ T: One half of the total number of students included in the item analysis Then, the criterion of discriminating power is rated as follows:
Table 3.1 The
Classification of Discriminating Power
2. Item Facility
Item facility refers an index of how easy an individual test item was for the people who took it.
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Item facility is typically printed in a decimal number and it represents the proportion of people or test takers who got the
item right. The reason why item facility must be concerned by test makers is to know whether an item is too easy or too difficult to answer.
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Kathleen M. Bailey, Learning about Language Assessment: Dillemas, Decisions, and Direction, London: Heinle Heinle Publisher, 1998, p. 132.
DISCRIMINATING POWER
REMARK
0.6 – 1.0
Very good 0.4
– 0.6 Good
0.1 – 0.3
Ok -1
– 0.0 Bad
To count the item facility of a test item, it will be used the following formula:
After the item facility has been counted, it can be known the rate of the difficulties and the easiness by using the item facility scale as follows:
Table 3.2 Item Facility Scale
IF REMARK
– 0.14 Difficult
0.15 – 0.85
Moderate 0.86
– 1.00 Easy
K. Criteria of the Action Success
Kategori