What is the value of the item-discrimination index for an item that all the students in the higher-scoring group answered correctly but that no one in the lower-scoring group answered correctly?
A) -1
B) +1
C) .50
D) .25

Question

Quizplus · Accepted Answer

The item discrimination index reflects the extent to which an individual item distinguishes between students who score high and low in the exam. When all students in the higher-scoring group answered correctly and no students in the lower-scoring group answered correctly, it indicates that the item clearly distinguishes between the two groups, resulting in a high discrimination index value. Therefore, the correct answer is B, which represents a perfect discrimination index of +1.

What Is the Value of the Item-Discrimination Index for an Item