Vector Psychometric Group (VPG) is proud to offer cutting-edge software for web-based data collection and item response data analysis. Authored by Li Cai, one of the leading experts in psychometrics, both Adaptest® and flexMIRT® have state-of-the-art features unavailable in other programs. Adaptest®, our web-based computerized adaptive testing (CAT) engine, has been updated to a “plug-in,” allowing any existing electronic data collection system (EDC) to administer adaptive tests and provide real-time scoring with minimal modifications. flexMIRT®, VPG’s item response theory (IRT) software, has some of the richest psychometric and statistical features currently available on the market today. With a point-and-click graphical user interface (GUI) and the ability to be called remotely, flexMIRT® is ideal for the individual analyses of an applied researcher or the large-scale analyses and scoring needed for operational use.


Adaptest® from VPG allows research teams to use a range of outcome measures from single-item responses to the most advanced item response theory-based assessments.  Adaptest® is easy to implement from full integration in the host system to a simple JavaScript plugin.  Adaptest® can run on any Microsoft or Linux system and easily scales on the Amazon Elastic beanstalk.  Regardless of the method, Adaptest® is able to easily integrate into most existing EDC systems, allowing them to administer items adaptively, if desired, and provide real-time scoring with minimal programming changes.


flexMIRT® (v. 3.5) is software specifically designed for the analysis of item response data, such as what can be obtained from a quality of life measure, attitude survey, or academic test. It is able to accommodate a wide variety of IRT models to factor structures that are both undimensional and multidimensional (e.g., the items measure more than one concept). flexMIRT® provides a wide variety of item and model fit statistics and indices for evaluating results and produces several different types of IRT-based scores, depending on user request. While flexMIRT® is primarily a confirmatory modeling program, it has newly added capabilities for performing EFA with analytic rotations as well.

Customized Software

VPG also offers clients the opportunity to customize Adaptest® or flexMIRT®, creating software that is built to meet your specific needs. Please contact us at for more information about how Adaptest® and flexMIRT® can be put to work for you.