Item analysis

ITEMANALYSIS

K.ARUNKUMAR M.Sc,M.Ed,M.Phil,

RESEARCH SCHOLAR S.R.K.V.COLLEGE OF EDUCATION

COIMBATORE2011-2012

ITEM ANALYSIS

Item analysis is a statistical technique

which is used for selecting and rejecting the

items of the test on the basis of their difficulty

value and discriminated power

OBJECTIVES OF ITEM ANALYSIS

To select appropriate items for the final draft

To obtain the information about the difficulty value(D.V) of all

the items

To provide discriminatory power (D.I) to differentiate between

capable and less capable examinees for the items

To provide modification to be made in some of the items

To prepare the final draft properly ( easy to difficult items)

STEPS OF ITEM ANAYSIS

Arrange the scores in descending order

Separate two sub groups of the test papers

Take 27% of the scores out of the highest scores and 27% of the

scores falling at bottom

Count the number of right answer in highest group (R.H) and

count the no of right answer in lowest group (R.L)

Count the non-response (N.R) examinees

Item analysis is done for obtaining:

a) Difficulty value (D.V)

b) Discriminative power (D.P)

DIFFICULTY VALUE (D.V)

“The difficulty value of an item is defined as the

proportion or percentage of the examinees who have

answered the item correctly”

- J.P. Guilford

The formula for difficulty value (D.V)

D.V = (R.H + R.L)/ (N.H + N.L)

• R.H – rightly answered in highest group

• R.L - rightly answered in lowest group

• N.H – no of examinees in highest group

• N.L - no of examinees in lowest group 

In case non-response examinees available means,

The formula for difficulty value (D.V)

D.V = (R.H + R.L)/ [(N.H + N.L)- N.R]

• R.H – rightly answered in highest group

• R.L - rightly answered in lowest group

• N.H – no of examinees in highest group

• N.L - no of examinees in lowest group

• N.R – no of non-response examinees

DISCRIMINATION INDEX (D.I)

“Index of discrimination is that ability of an

item on the basis of which the discrimination

is made between superiors and inferiors”

- Blood and Budd

(1972)

TYPES OF DISCRIMINATION INDEX (D.I)

Zero discrimination or No discrimination

Positive discrimination

Negative discrimination

ZERO DISCRIMINATION OR NO DISCRIMINATION

The item of the test is answered correctly or know the answer by all the examinee’s

An item is not answered correctly any of the examinee

POSITIVE DISCRIMINATION INDEX

An item is correctly answered by superiors and is

not answered correctly by inferiors. The

discriminative power range from +1 to -1.

NEGATIVE DISCRIMINATION INDEX

An item is correctly answered by inferiors and is

not answered correctly by superiors.

The formula for discrimination index(D.I)

D.I = (R.H - R.L)/ (N.H or N.L)

• R.H – rightly answered in highest group

• R.L - rightly answered in lowest group

• N.H – no of examinees in highest group

• N.L - no of examinees in lowest group

Another method for discrimination index(D.I)

If you take Likert scale for data collection

The correlation between each item scores with total scores.

General guidelines for discriminating index (D.I)

According to Ebel ,

D.I Item Evaluation

≥0.40 Very good items

0.30 - 0.39 Reasonably good but subject to improvement

0.20 – 0.29 Marginal items , need improvement

<0.19 Poor items . Rejected or revised

General guidelines for difficulty value (D.V)

Low difficulty value index means, that item is high difficulty one ex: D.V=0.20 » 20% only answered correctly for that item. So that item is too difficult

High difficulty value index means, that item is easy one

ex: D.V=0.80 » 80% answered correctly for that item. So that item is too easy one

D.V Item Evaluation

0.20 – 0.30 Most difficult

0.30 - 0.40 Difficult

0.40 – 0.60 Moderate difficult

0.60 – 0.70 Easy

0.70 – 0.80 Most easy

Relationship between difficulty value and discrimination power

Both (D.V & D.I) are complementary not contradictory to each other

Both should considered in selecting good items

If an item has negatively discriminate or zero discrimination, is to be

rejected whatever the difficulty value 

CRITERIA FOR SELECTION AND REJECTION ITEMS

Positive discrimination index only selected

Negative and zero discrimination index items are

rejected

High and low difficulty value items are rejected

REFERENCE

Sharma R.A (2007);Essential of Scientific Behavioural

Research, Meerut, Lall book depot.

Mehta D.D (2011);Educational Measurement and Evaluation,

Meerut, Tandon publication.

Kulbir Singh Sidhu (2005);New Approaches to Measurement

and Evaluation, New Delhi, Sterling Publishers.

Akbar Husain (2012);Psychological Testing, New Delhi, Pearson.

Thank you