多年的SSI已經有了廣泛分佈套房四IRT （項目反應理論）稱為BILOG -MG ， MULTILOG ， Parscale和Testfact方案。然而，隨著成長和成功也帶來新的用戶和新的期望。儘管取得了成功，這些IRT程序是遠遠不夠完善以今天的軟件的標準來衡量。此外，它們共享了大量的相似性和重疊的功能的。因此，可以明顯看出一個國家的最先進的單，軟件產品必須開發，以取代這四個程序。
為了努力滿足廣大用戶群體的不斷增長的需求， SSI公司開發一個新的軟件產品，名為IRTPRO ，這是對當前技術的最前沿。該方案已被廣泛的測試在Microsoft Windows平台的Windows7 ， Vista和XP操作系統上。該IRTPRO數字引擎的重要路段已同時並行在多個內核上運行。
IRTPRO同時支持基於模型和基於數據的圖形顯示。基於模型的圖形，目前僅適用於單維IRT模型，是軌跡線，信息的曲線，結合軌跡線信息的曲線，全面的信息，以及測試特性曲線。
從各種統計軟件包IRTPRO進口數據以及從固定格式數據導入數據（固定的） ，逗號分隔（ CSV ） ，製表符分隔（通常， TXT ） ，和Excel （ xls）的文件。無論原來的格式，導入的數據保存到擴展名為一個IRTPRO數據文件。 SSIG是視覺上顯示為一個表格，在外觀到Excel電子表格相似。
In an effort to meet the growing demands of our user community, SSI has developed a new software product, called IRTPRO, which is on the cutting edge of current technology. The program has been tested extensively on the Microsoft Windows platform with Windows7, Vista and XP operating systems. Important sections of the IRTPRO numeric engine have been parallelized to run on multiple cores simultaneously.
IRTPRO supports both model-based and data-based graphical displays. Model-based graphs, currently available for unidimensional IRT models only, are trace lines, information curves, combined trace lines-information curves, total information, and test characteristic curves.
IRTPRO imports data from a variety of statistical software packages as well as importing data from fixed format data (.fixed), comma-separated (.csv), tab-delimited (usually .txt), and Excel (.xls) files. Whatever the original format, the imported data are saved to an IRTPRO data file with extension .ssig that is displayed visually as a spreadsheet, similar in appearance to an Excel spreadsheet.
Unidimensional and multidimensional (confirmatory or exploratory) versions of the following widely used response functions: Two-parameter logistic (2PL) [includes the one-parameter logistic (1PL) with equality constraints], Three-parameter logistic (3PL), Graded, Generalized Partial Credit, and Nominal.