Item Analysis Prof. Trevor Gibbs

Item Analysis After you have set your assessment: How can you be sure that the test items are appropriate?—Not too easy or too difficult Will the test differentiate between those students who do well and those who do not ?

Item Analysis Difficulty Index Discrimination Index Point biserial coefficient Reliability index

Item Analysis Difficulty Index ( difficulty level of test items) Proportion who have answered the test item correctly ( 100% = easy, 0% = hard ) ( >75% = easy, <25% = hard ) QuestionABCDE * * *4505

Item Analysis Discrimination Index: -differentiation between high and low scorers “ High performing students should select the correct answer more often than low performing students ” Positive discrimination index ( between 0 and 1 ) Negative discrimination index ( between -1 and 0 )

Item Analysis StudentTotal score (%)A B C a b c d e f g h i j

Item Analysis Discrimination Index: Subtract the number of students in the lower group who got the answer right from the number in the upper group who got the answer right Divide by the number in each group

Item Analysis Question Difficulty Discrimination index index A 80 0 B C 600.8

Item Analysis Point Biserial Coefficient: Correlation between score on the item and score on the total examination. A positive value indicates that examinees who answered the item correctly scored relatively higher on the whole examination. A negative value indicates that examinees who answered the item correctly scored relatively lower on the whole examination