项目反应理论(Item Response Theory，简称IRT)包括一组分析套装软件: BILOG-MG, MULTILOG, PARSCALE, and TESTFACT。

试题反应理论(IRT)的应用
编制测验(量表)
测验等化
建立题库
组合测验
电脑化适性测验

这些软件可作为题目分析以及分数估计等方面的重要工具，并且在各个领域被广泛应用。

BILOG-MG是适用于二元计分(对与错)试题logistic模式之试题参数及考生能力之估计的套装软体。由美国Scientific Software, Inc发行，能处理单参数、二参数及三参数模式的资料。 BILOG-MG使用的统计法有可供选择：
最大相似法(Maximum Likelihood)
后面期望的贝氏法(Expected A Posteriori)
后面最大的贝氏法(Maximum A Posteriori)

功能:

Graphical user interface

Efficient analysis of binary items including multiple choice or short-answer items scored right, wrong, omitted, or not-presented
Capable of large scale production analysis, and handling of multiple groups
Performs item analysis and scoring of any number of subtests or subscales
Non-equivalent groups equating
Vertical equating of test forms
Differential item functioning (DIF)
Detection and correction for parameter trends over time (DRIFT)
Calibration and Scoring of tests in two-stage testing procedures
Estimation of latent ability or proficiency distributions
Provision for items inserted in tests to estimate item statistics, but not included in calculation of examinee scores ("variant items")
Item fit statistics, theoretical and empirical reliability
Information curves and reliabilities for putative test forms
Presentation quality IRT graphics, can be imported in Word, Access, etc.
Detailed online HELP documentation includes description of interface, syntax, and examples.