Module 6 – Analyzing and Using Test Item Data

The purpose of Test Item Analysis is to select the best available items for the final form of the test, to identify structural or content defects in the items, to detect learning difficulties of the class as a whole and to identify the areas of weaknesses of students in need of remediation. The three Elements in an Item Analysis are Examination of the difficulty level of the items, Determination of the discriminating power of each item, and Examination of the effectiveness of distracters in a multiple choice or matching items.

The difficulty level of an item is known as index of difficulty. Index of difficulty is the percentage of students answering correctly each item in the test Index of discrimination refers to the percentage of high-scoring individuals responding correctly versus the number of low-scoring individuals responding correctly to an item. This numeric index indicates how effectively an item differentiates between the students who did well and those who did poorly on the test.

Using Information about Index of Discrimination The index of discrimination tells a teacher the degree to which a test item differentiates the high achievers from the low achievers in his class. A test item may have positive or negative discriminating power. An item has a positive discriminating power when more students from the upper group got the right answer than those from the lower group. When more students from the lower group got the correct answer on an item than those from the upper group, the item has a negative discriminating power.

There are instances when an item has zero discriminating power – when equal number of students from upper and lower group got the right answer to a test item. In the given example, item 5 have the highest discriminating power. This means that it can differentiate high and low achievers.

A test item can be retained when its level of difficulty is average and discriminating power is positive. It has to be rejected when it is either easy/very easy or difficult/very difficult and its discriminating power is negative or zero. An item can be modified when its difficulty level is average and its discrimination index is negative.

Examining Distracter Effectiveness is an ideal item is one that all students in the upper group answer correctly and all students in the lower group answer wrongly. And the responses of the lower group have to be evenly distributed among the incorrect alternatives.

Developing an item data file encourage teachers to undertake an item analysis as often as practical Allowing for accumulated data to be used to make item analysis more reliable. Providing for a wider choice of item format and objectives. Facilitating the revision of items. Facilitating the physical construction and reproduction of the test. Accumulating a large pool of items as to allow for some items to be shared with the students for study purposes.

 The Limitations of Item Analysis is: It cannot be used for essay items. Teachers must be cautious about what damage may be due to the table of specifications when items not meeting the criteria are deleted from the test. These items are to be rewritten or replaced.