Intro to IRT

Michael J. Zickar, Ph.D.

Department of Psychology, Bowling Green State University






John Uebersax's webpage which provides background information on IRT (latent trait analysis--LTA).  Sections include:  What LTA Can Do, Basic Readings, Issues (model choice), and Links.  A section on latent trait models for rater agreement is also given.

Penn State's University Test Center.  This page includes a basic description of classical test theory compared to IRT and includes background information on the 3PL, estimating ability, and test construction.

This is a similar page that describes classical test theory.

Dr. Michael Brannick's homepage.  This includes a description of IRT that is based on the 3PL.  There are nice illustrations on how various parameters determine the shape of the 3PL item response function.

This is the site to check out for Rasch modeling and related applications.  It is run by the Institute for Objective Measurement at the University of Chicago  Highly recommended!

Annotated Bibliography

General Introductions

Drasgow, F., & Hulin, C. L.  (1990).  Item response theory.  In M. D. Dunnette & L. M. Hough (Eds.), Handbook of Industrial and Organizational Psychology, Vol. I (pp. 577-636).  Palo Alto, CA: Consulting Psychologists Press.

A very good introduction to IRT.  This chapter covers all of the basics including models, estimation, applications, the like.  Applications are geared to industrial-organizational psychologists, though, this chapter would be an appropriate introduction for most audiences.  Unlike most introductions to IRT, this chapter includes discussion of non-parameteric models and appropriateness measurement.

Hambleton, R. K., & Swaminathan, H.  (1985).  Item response theory: Principles and applications.  Boston: Kluwer-Nijhoff.

Hambleton, R. K., Swaminathan, H., Rogers, H. J.  (1991).  Fundamentals of Item Response Theory.  Newbury Park, NJ:  Sage.   

This is a great, cheap introduction to IRT.  This is often the first source that I suggest to students when they express interest in IRT.  Basic concepts are covered.

Lord, F. M.  (1980).  Applications of item response theory to practical testing problems.  Hillsdale, NJ:  Erlbaum.

This book is easier to read than Lord & Novick (1968) though it is outdated in many places.  Material includes concise descriptions of classical test theory and IRT and descriptions of applications of IRT.  These include tailored testing, mastery testing, estimating ability, equating, test bias, and others.  The application chapters are excellent in providing a good foundation but are outdated given the advances that have been made since the book was initially published. 

Lord, F. M., & Novick, M.  (1968).  Statistical theories of mental test scores.  Reading, MA:  Addison-Wesley.

The classic treatment on classical test theory.  A very challenging read, though well worth spending time with.  Advanced graduate students only.  The last section of the book includes material written by Birnbaum on the dichotomous logistic models.   Unfortunately this book is out of print.

Zickar, M. J.  (1998).  Modeling item-level data with item response theory.  Current Directions in Psychology, 7, 104-109.

A quick and dirty introduction to IRT written for a non-measurement audience.  Appropriate for an applied measurement seminar with minimal discussion on IRT.  For more in-depth treatment of IRT, there are better introductions.