2. This lesson is designed to help you do
three things:
To interpret the test items
To differentiate
between well-
performing items and
poor-performing items
To make decisions about
poor performing items
3. We give tests for 4 primary reasons.
To find out if students
learned what we intended
To separate those who
learned from those who
didn’t
To increase learning and
motivation
To gather information for
adapting or improving
instruction
Why we give test and interpret it?
4. All you need to know about it.
Terminologies
Difficulty
indexDiscrimination
index
Distracter
Analysis
5. Why do we need to
analyze the items of the
test paper?
6. What is Item Analysis?
* Item Analysis can help you
evaluate how well your
objective items are actually
working.
*These problems can be
corrected, resulting in a
better test, and better
7. Continued...
* Refers to a statistical
technique that helps
instructors/teachers
identify the
effectiveness of their
test items.
8. Difficulty Index
• Indicates the proportion of
students who got the item
right.
• A high percentage
indicates an easy
item/question and a low
percentage indicates a
difficult item.
9. Continued...
* In general items should
have values of difficulty no
less than 20% correct and
no greater than 80%.
10. Item Difficulty Level: Examples
Item
No.
No. Correct
Answers
% Correct Difficulty
Level
1 15
2 25
3 35
4 45
Number of students who answered each item = 50
30 High
50 Medium
70 Medium
90 Low
11. Were any of the items too difficult or too
easy?
How to use the Difficulty Factor of a question
Proportion of respondents selecting the right
answer to that item
D = c / n
D = difficulty factor
c = number of correct answers
n = number of respondents
Range 0 -1
The HIGHER the difficulty factor – the easier the
question is, so a value of 1 would mean all the
students got the question correct and it may be
too easy
12. Let’s Practice
What is the D for Items 1-3
Student
Raw
score Item 1 Item 2 Item 3 Item 4 Item 5
A 8 a b a d e
B 6 c b e c e
C 6 a c e c b
D 4 a b e a c
E 2 c a b d c
F 8 a b c c e
G 10 a b a c e
H 6 a b c d e
I 8 a c a c e
J 4 a c a d b
13. Difficulty results
Item # 1 = .8
Item # 2 = .6
Item # 3 = .4
What does it mean?
Item # 1 = .8 may be too easy
Item # 2 = .6 good
Item # 3 = .4 good
14. Difficulty results continued…
Item # 4 = .5
Item # 5 = .6
What does it mean?
Item # 4 = .5 optimal
Item # 5 = .6 good
Overall, you can say that only item #1
may be too easy
15. Discrimination Index
- This is a number which
indicates the ability of an
item to differentiate
between high and low
scorers on the test.
16. A-B
n
Do the items discriminate between those students
who really knew the material from those that did
not?
The Discrimination Index formula
DI = (a-b) / n or D=
a=response frequency of the High
group
b=response frequency of the Low
group
n-number of respondents
17. Guide for interpreting discrimination
index
0.0 –negatively or not at all
discriminating
.01 - .15 – very low
discrimination
.16 - .30 – moderately
discrimination
.31- .45 – good discrimination
> . 45 – highly discrimination
18. Item Discrimination: Examples
Item
No.
Number of Correct Answers
in Group
Item
Discrimination
IndexUpper 1/4 Lower 1/4
1 90 20
2 80 70
3 100 0
4 100 100
5 50 50
6 20 60
0.7
0.1
1
0
0
-0.4
Number of students per group = 100
19. Distracter Analysis
It is another useful step in reviewing the
effectiveness of a test item.
All of the incorrect options, or distracters,
should actually be distracting.
In order for distracter to be acceptable it
should attract at least one candidate.
If no one selects a distractor it is important to
revise the option and attempt to make the
distractor a more plausible choice.
20. How many inches are in a foot?
A. 6
B. 12
C.24
D.100
Stem
Distracters
Key
Options
Multiple choice items are comprised of 4 basic
components.
21. Distracter Analysis: Examples
Item 1 A* B C D E Omit
% of students in upper ¼ 20 5 0 0 0 0
% of students in the middle 15 10 10 10 5 0
% of students in lower ¼ 5 5 5 10 0 0
(*) marks the correct answer.
Item 2 A B C D* E Omit
% of students in upper ¼ 0 5 5 15 0 0
% of students in the middle 0 10 15 5 20 0
% of students in lower ¼ 0 5 10 0 10 0
