1. Lesson Nine
Item Analysis

2. Contents Item Difficulty Item Discrimination
Distractor (efficiency) analysis

3. Item Difficulty (Item Facility)
Difficulty index: P or IF
In terms of how many people got this item correct (i.e., the percentage of Ss who correctly answer a given item).
P= The number of correct responses divided by the number of total test takers.
0 ≤ P ≤ 1 (0= difficult item, 1= easy item)
Achievement Test (CRT): P=0 or P= 1  possible
NRT: P=0 or P=1  means the designer has to go back and check the question

4. Item Discrimination Discrmination index: ID or D
Indicate the degree to which the task differentiates correctly among test takers; the difference of the percentage passing between upper group and lower group
Sharper discrimination when using extreme ends but the sample is small
Correct Answer in Upper Group – Correct Answer in Lower Group
No. of people in each group (one group)

5. Distractor (Efficiency) Analysis
To investigate the degree to which the distractors are functioning efficiently.
Specifically related to the multiple-choice format.