ANALYZING AND USING TEST ITEM DATA

Preparing Data for Item AnalysisArrange test scores from highest to lowest.

Get one-third of the papers from the highest scores and the other third from the lowest scores.

Record separately the number of times each alternative was chosen by the students in both groups.TableAdd the number of correct answers to each item made by the combined upper and lower groups.

Compute the index of difficulty for each item, following the formula:IDF = (H+L/N)100

Where IDF = index of difficulty H+L = number of students responding correctly to an item N = total number of students in the upper and lower groups

TableCompute the index of discrimination, based on the formula:IDN = (H L) N/2Where IDN = index of discriminationH = number of correct responses of the upper groupL = number of correct responses of the lower groupN/2 = number of students per group

TableIndex of Difficulty and Index of DiscriminationThe difficulty level of an item is known as index of difficultyIndex 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 DifficultyThe difficulty index of a test item tells a teacher about the comprehension of or performance on material or task contained in an item.ItemGroupAnswers

A B C DTotal No. of Correct AnswersH+LDifficulty Index=(H+L / N)*100H L DiscriminationIndex= (H L) N/2

1H 20

L 203 14 2 1

10 7 3 02152.570.352H 20

L 200 0 18 2

0 3 9 82767.590.453H 20

L 203 8 4 4

10 2 4 41025.060.304H 20

L 203 3 4 10

2 4 10 41435.060.305H 20

L 20 2 2 1

1 10 4 51640.0140.70567For an item to be considered a good item, its difficulty index should be 50%. An item with 50% difficulty index is neither easy nor difficult.

If an item has a difficulty index of 67.5%, this means that it is 67.5% easy and 32.5% difficult.

Information on the index of difficulty of an item can help a teacher decide whether a test should be revised, retained or modified.Interpretation of the Difficulty IndexRangeDifficulty Level20 & below21 4041 6061 8081 & aboveVery DifficultDifficultAverageEasyVery Easy

TableUsing Information about Index of DiscriminationThe 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 groupWhen 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 has the highest discriminating power. This means that it can differentiate high and low achievers.TableInterpretation of the Index of DiscriminationRangeVerbal Description.40 & above.30 .39.20 .29.09 .19Very Good ItemGood ItemFair ItemPoor Item

TableWhen should a test item be rejected? Retained? Modified or revised?It can be retained when its level of difficulty is average and discriminating power is positive

It can be rejected when it is either easy/very easy or difficult/very difficult and its discriminating power is negative or zero

It can be modified when its difficulty level is average and its discrimination index is negativeTableExamining Distractor EffectivenessAn 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 alternativesSample Item Analysis Table for Studying Distractor In A Multiple Choice ItemGroupGroup SizeResponse Alternatives1234OmitTest ItemHigh Scoring1044200Low Scoring1052102SuspectNeeds ImprovementDanger SignalShould be discarded ImprovementDeadwoodMust be replaced