Free irt tools

The first free irt tool from www.irtportal.com has been released. It is an excel spreadsheet prepared to let researchers and students easily observe the change in item response functions (IRF), item information functions (IIF) and the hypothetical Standard Error (SE) values attributed to these IIFs with the change in the item parameters. The program is based on 3 Parameter Logistic Model (3PLM). However, similar IRFs and IIFs in 2 Parameter Logistic Model (2PLM) can be obtained if "c" parameter is set to "0". Accordingly, if "a" parameter is fixed to "1" and "c" is fixed to "0", IRFs and IIFs similar to 1 Parameter Logistic Model (1PLM) can be obtained. For more information about the program and some screenshots, please click here.