This workshop provides a practical introduction to Item Response Theory (IRT), a powerful set of tools for measuring latent traits. Central characteristics of IRT are that the trait or ability of the person is decoupled from the properties of the test items and that its assumptions can be empirically tested. IRT has been state of the art in large scale educational assessments for quite some time now and is becoming more and more common in all other areas of psychological assessment, too, both for empirically validating newly suggested psychological tests as well as for investigating the measurement properties of existing instruments.

The workshop has two goals. First, it will briefly review the theory behind common IRT models like the Rasch model and Birnbaum's 2PL model. Second, it will show participants how to practically fit these models in R by means of hands-on exercises. The workshop will close with a short outlook on more recent developments in IRT that are also available in R.

For the practical exercises, the participants bring their own laptops to the workshop and will be instructed in advance which free R package they need to install. Previous experience with R is helpful but not mandatory.