This is the webpage for the handbook on differential item functioning.
Zumbo, B. D. (1999). A Handbook on the Theory and Methods of Differential
Item Functioning (DIF): Logistic Regression Modeling as a Unitary Framework
for Binary and Likert-type (Ordinal) Item Scores. Ottawa ON: Directorate
of Human Resources Research and Evaluation, Department of National Defense.
Because I wrote the Handbook under a research contract from the Department of National
Defense (DND) of Canada, the DND is distributing it free of charge for
purposes of research and teaching.
The Handbook is in PDF format and can be
accessed with Acrobat Reader. The example data files and SPSS syntax command
files are also available below.
If you prefer a bound hardcopy of the handbook please contact Professor
Zumbo via e-mail. The e-mail address is listed below.
If you have problems retrieving any of the files below or you want to contact Professor Zumbo
at the Edgeworth Laboratory for
Quantitative Educational & Behavioral Science, you can do so by the
or via Internet e-mail: firstname.lastname@example.org.
Click this icon,
to download the free software to read PDF files.
1. To access (for printing or reading on screen) a copy of the Handbook with Adobe Acrobat Reader please click
2. To download a copy of the SPSS syntax files and the example data sets,
please right mouse click | save link as (any file type), and save it to
your local harddrive.
Create a subdirectory entitled 'binary' on your local drive. Right mouse
click and save these file to the 'binary' subdirectory.
Create a subdirectory entitled 'ordinal' on your local drive. Right mouse
click and save these file to the 'ordinal' subdirectory.
- 2 b. For Likert-type (ordinal) items