ItemAnalysi

sand

Validation

Introduction The teacher normally

prepares a draft of the test. Such a draft is subjected to item analysis and validation to ensure that the final version of the test would be useful and functional.

Phases of preparing a testTry-out phaseItem analysis phaseItem revision phase

Characteristic of an Item

Item DifficultyDiscrimination Index

Item Difficultydefined as the

number of students who are able to answer the item correctly divided by the total number of students.

ItemDifficulty=

# of students w/ correct answer

total number of students

Example: What is the item difficulty index of an item if 25 students are unable to answer it correctly while 75 answered it correctly?

Range of difficulty index

Interpretation Action

0 – 0.25 DifficultRevise or discard

0.26 – 0.75 Right difficulty retain

0.76 - above EasyRevise or discard

Difficult items tend to discriminate between those who know and those who does not know the answer.

Easy items cannot discriminate between those two groups of students.

An easy way to derive such a measure is to measure how difficult an item is with respect to those in the upper 25% of the class and how difficult it is with respect to those in the lower 25% of the class.

IndexOf

Discrimination= DU-DL

Obtain the index of discrimination of an item if the upper 25% of the class had a difficulty index of 0.60 while the lower 25% of the class had a difficulty index of 0.20.

Example:

The index of discrimination can range from -1.0

(when DU =0 and DL = 1)

to 1.0

(when DU = 1 and DL = 0).

Index Range Interpretation Action

-1.0 to -.50Can discriminate but the item is questionable

Discarded

-.55 to .45Non-

discriminatingRevised

.46 to 1.0Discriminating

itemInclude

Example: Consider a multiple item choice type of test with the ff. data were obtained:

*The correct response is B.

Item Options

1

A B* C D

0 40 20 20 Total

0 15 5 0 Upper 25%

0 5 10 5 Lower 25%

ItemDifficulty =

# of students w/ correct answer

total number of students

= 40

100

= 40% (within of a “good item”)