This is the webpage for the handbook on differential item
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
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 hard copy 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 post
or via Internet e-mail: email@example.com.
1. To access (for printing or reading on screen) a copy of the Handbook
with Adobe Acrobat Reader please click .
2. A copy of the SPSS syntax files and the example data sets are
available in a compressed (zipped file) can be found here.
3. You can also download a more recent description by Slocum, Gelin,
and Zumbo of how to do DIF analyses in SPSS here.
If you have difficulty downloading files, please contact Professor
Zumbo at e-mail: firstname.lastname@example.org
Updated: September 1, 2017