ITEM ANALYSIS
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Transcript of ITEM ANALYSIS
ITEM ANALYSIS
It 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.
ITEM ANALYSIS
Try-out phaseItem analysis phaseItem revision phase
Phases of preparing a test
Two characteristics of an item:
Item DifficultyDiscrimination Index
Item Difficulty“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
I.D = no. of students with the correct ans.
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 Difficult Revise or discard
0.26 – 0.75 Right difficulty retain
0.76 - above Easy Revise or discard
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
“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)
Index of Discrimination
Types of discrimination index (D.I)
Zero discrimination or No discrimination
Positive discrimination
Negative discrimination
Index Range Interpretation Action
-1.0 to -.50 Can discriminate but the item is questionable
Discarded
-.55 to .45 Non-discriminating
Revised
.46 to 1.0 Discriminating item
Include
STEPS in getting I.D
Arrange the scores in descending order
Separate two sub groups of the test papers
Get 25% of the scores out of the highest
scores and 25% falling at bottom
Count the number of students who got
answer correctly in both groups.
Discrimination index = DU – DL
Example: Consider a multiple item choice type of test with the ff. data were obtained:
Item Options
1A B* C D
0 40 20 20 Total
0 15 5 0 Upper 25%
0 5 10 5 Lower 25%
The discrimination index can be similarly be computed:
DU = no. of students in the upper 25% with correct response
No. of students in the upper 25%
=15/20 = .75 or 75%
DL= no. of students in lower 75% with correct response
no. of students in the lower 25%
= 5/20 = .25 or 25%
Discrimination index = DU – DL
= .75 - .25
= .50 or 50%`
FORMULAS
Index of Difficulty
P= RU + RL
T
Index item Discriminating Power
D= RU + RL
½ T
100
100
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