Lesson NineLesson Nine

Item AnalysisItem Analysis

ContentsContents

Item DifficultyItem Difficulty Item DiscriminationItem DiscriminationDistractorDistractor (efficiency) analysis (efficiency) analysis

Item Difficulty (Item Facility)Item Difficulty (Item Facility)Difficulty index: P or IFDifficulty index: P or IF In terms of how many people got this item In terms of how many people got this item

correct (i.e., the percentage of Ss who correct (i.e., the percentage of Ss who correctly answer a given item).correctly answer a given item).

P= The number of correct responses P= The number of correct responses divided by the number of total test takers.divided by the number of total test takers.

0 0 ≤ P ≤ 1 (0= difficult item, 1= easy item)≤ P ≤ 1 (0= difficult item, 1= easy item)Achievement Test (CRT): P=0 or P= 1 Achievement Test (CRT): P=0 or P= 1

possiblepossibleNRT: P=0 or P=1 NRT: P=0 or P=1 means the designer has means the designer has

to go back and check the questionto go back and check the question

Item DiscriminationItem Discrimination

Discrmination index: ID or DDiscrmination index: ID or D Indicate the degree to which the task differIndicate the degree to which the task differ

entiates correctly among test takers; the dientiates correctly among test takers; the difference of the percentage passing betweefference of the percentage passing between upper group and lower groupn upper group and lower group

Sharper discrimination when using extremSharper discrimination when using extreme ends but the sample is smalle ends but the sample is small

Correct Answer in Upper Group – Correct Answer in Lower Group

No. of people in each group (one group)

Distractor (Efficiency) AnalysisDistractor (Efficiency) Analysis

To investigate the degree to which the distTo investigate the degree to which the distractors are functioning efficiently.ractors are functioning efficiently.

Specifically related to the multiple-choice fSpecifically related to the multiple-choice format.ormat.