2. 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
discriminating power
Item analysis is done for obtaining: Difficulty
value (D.V) Discriminative power (D.P)
3. 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
4. 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
5. 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
6. 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
7. 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
8. Zero discrimination or No 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 by any of the examinee
Positive discrimination index:
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:
Negative discrimination index :An item is correctly answered by inferiors and
is not answered correctly by superiors.
9. 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
10. 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
11. 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 be considered in selecting good items
If an item has negatively discriminate or zero discrimination, is to be
rejected whatever be the difficulty value
