BILOG-MG Operational is the only license type available for purchase. With an annual license fee of $10,600, the operational license covers purpose such as test/assessment calibration, scoring, linking or standard setting for a client, product, or student/employee evaluation.


BILOG-MG is an extension of BILOG that is designed for the efficient analysis of binary items, including multiple-choice or short-answer items scored right, wrong, omitted, or not-presented. BILOG-MG is capable of large-scale production applications with unlimited numbers of items or respondents. It can perform item analysis and scoring of any number of subtests or subscales in a single program run. All the program output may be directed to text files for purposes of selecting items or preparing reports of test scores.

BILOG-MG implements an extension of Item Response Theory (IRT) to multiple groups of respondents. It has many applications in test development and maintenance. Applications of multiple-group item response theory in education assessment and other large-scale testing programs include the following features.

  • Nonequivalent groups equating for maintaining the comparability of scale scores as new forms of the test are developed.
  • Vertical equating of test forms across school grades or age groups.
  • Analysis of Differential Item Functioning (DIF) associated with demographic or other group differences.
  • Detecting and correcting for item parameter trends over time (DRIFT).
  • Calibrating and scoring tests in two-stage testing procedures designed to reduce total testing time.
  • Estimating latent ability or proficiency distributions of students in schools, communities, or other aggregations.

In addition, BILOG-MG provides for variant items that are inserted in tests for purpose of estimating item statistics, but that are not included in the scores of the examinees.


A list of examples discussed in the BILOG-MG Guide is given below, along with extra examples and a zip file containing all examples and data.

Conventional single-group IRT analysis (complete example zipped)

Differential item functioning (complete example zipped)

Equivalent groups equating (complete example zipped)

Vertical equating (complete example zipped)

Multiple matrix sampling data (complete example zipped)

Analysis of variant items (complete example zipped)

Group-wise adaptive testing (complete example zipped)

Estimating and scoring tests of increasing length (complete example zipped)

Commands for parallel-form correlations (complete example zipped)

EAP scoring of the NAEP forms and state main and variant tests (complete example zipped)

Domain scores (complete example zipped)

Extra examples (zipped)


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