IRT DIF Graphing Tool

The IRT DIF Graphing Tool is an Excel spreadsheet designed to help you visualize and evaluate the presence of differential item functioning (DIF) based on item response theory (IRT).  It is meant as a post-hoc tool for analysis that is done with other software, such as DFIT.

How does it work?

1.  Analyze DIF with specialized software like DFIT or PARSCALE.  You will have output that gives item parameters for your two groups.
2.  Paste the item parameters into this spreadsheet.
3.  Evaluate the graphics – they will all populate in real time, no configuration or “running” of a program required.