Steps in
Creating Short Forms of IQ Tests
(Quick, Dirty, and
Not Recommended)
In order to develop the statistics
for a short form, the reliability coefficient and intercorrelation of
each subtest must be determined.
Step 1: Choose a Short
Form
Create a table that lists the
reliability of each chosen subtest along with the correlation matrix
for those same subtests. For example, suppose you want a fivesubtest
short form for the WISCIII that uses Information (I), Vocabulary
(V), Picture Completion (PC), Coding (Cd), and Block Design (BD)
[the short form developed by Dumont
and Faro]. The table
below was created adapting information provided in the WISCIII
manual. (The relevant columns are numbered 1 through 6 and the
relevant rows are lettered A through F.)

1


2

3

4

5

6


r







A

.84

I

I

V

PC

Cd


B

.87

V

.70





C

.77

PC

.47

.45




D

.79

Cd

.21

.26

.18



E

.87

BD

.48

.46

.52

.27


F

4.14


1.86

1.17

.70

.27

4.00

Step 2: Determine the Sum of
Reliabilities
Add the reliabilities in column 1
(rows A through E) to obtain the sum of the reliabilities. In this
case the sum is equal to 4.14 (Column 1, row F).
Step 3: Determine the Sum of
Intercorrelations
Add all of the intercorrelations. In
this case they are equal to 4.00 (Column 6, row F).
Step 4: Determine the
Multiplier and Additive
Using the number obtained in Step 3,
obtain the Multiplier and the Additive for your subtest combinations
from the appropriate tables linked below.
Table
for Twosubtest short form
Table
for Threesubtest short form
Table
for Foursubtest short form
Table
for Fivesubtest short form
In the example above, we are making
a fivesubtest short form, so I would go to the Table
for Fivesubtest short form
and look up the numbers associated with the value of 4.00. I find the
correct Multiplier and Additive in the section that looks
like:
3.793.96

1.4

30

3.974.15

1.4

31

4.164.35

1.4

32

4.364.56

1.3

35

The numbers are 1.4 and 31. To
determine a deviation quotient for the proposed short form, add
together the subtest scaled scores, multiply that sum by 1.4, and
finally add 31 to the product.
In our example, substituting subtest
scaled scores, the five subtests Short form would be:
(I+V+PC+Cd+BD)*1.4+31
(10+9+10+10+5)*1.4+31
(44)*1.4+31
61.6+31
Deviation Quotient = 92.6
Step 5: Determine the
reliability of the short form by using the following
formula
Reliability=
Sum of reliabilities + 2 (Sum of Intercorrelations)
Number of Subtests + 2 (Sum of Intercorrelations)
For our example the reliability
would be:
4.41 + 2(4.0)
5 + 2(4.0)
The reliability is
.93.
Step 6: Determine the Standard
Error of Measurement
Standard error of Measurement =
Confidence level * Standard Deviation * Square Root
(1Reliability)
Confidence levels:
1.64 = 90%
1.96 = 95%
For our example:
1.96*15*Sqrt(1.93)
SEm=7.6
•
Dumont, R. & Faro, C. (1993) WISCIII Short Form for Learning
Disabled Children. Psychology in the Schools., 30, 212219
