IRT Modeling Lab
Welcome to UIUC IRT Modeling Lab's tutorial on item response theory (IRT). On this web site, we provide basic information that will help you begin using IRT methods in your research. Please click here if the menu bar is not shown on the left.

Additional information on IRT is widely available in books and journal articles. When necessary, we provide references for readers interested in more detail.

Our tutorial is divided into 8 major sections. Links to each of them are as follows:

A. Introduction to IRT

This section will present an introduction to Item Response Theory.

B. Data Preparation for IRT Analyses

This section will show you how to prepare raw data for typical IRT analyses.

C. Investigation of Dimensionality

This section briefly describes how to assess the dimensionality of your data.

D. Estimation of IRT Model Parameters

Procedures on how to estimate item parameters for dichotomous and polytomous IRT models.

E. Assessment of Model-data Fit

An introduction to graphical and statistical methods for assessing model-data fit.

F. Detection of Differential Item/Test Functioning (DIF/DTF) Using IRT

Investigating item/test bias across subpopulations of examinees.

G. Test Construction: Creating Parallel Forms

This section will contrast classical test theory approachs to the test construction with IRT-based approaches.

H. FAQ (Frequently Asked Questions)

This section provides answers to some frequently asked questions, compiled and answered by Ben-Roy Do. If you have IRT tutorial web site related questions, you may send an e-mail to the webmaster.

Please use the menu bar on the left to tour each section.