All posts by Janel Kinlaw

Introducing IRTPRO™ Version 5.0

VPG is pleased to announce that with the acquisition of Scientific Software International, Inc. in early 2020, IRTPRO™ Version 5.0 is being released under a new subscription-based software delivery and support model. A popular IRT software program for both patient-reported outcomes analysis and educational assessment development, this latest upgrade release offers significant new features and improvements.  Please visit to find out more about IRTPRO™.  Visit our storefront at to learn more about licensing and to make a purchase.

VPG Releases flexMIRT® 3.6 Release Candidate

VPG is pleased to announce the availability of flexMIRT® Version 3.6 Release Candidate, which can be obtained through our webstore. flexMIRT® Version 3.6 offers an improved user-friendly GUI and substantially upgraded statistical modeling capabilities, including new model fit indices, multidimensional models with non-normal latent densities, Markov chain Monte Carlo (MCMC) estimation, crossed random effects, and improved diagnostic classification modeling.

Vector Psychometric Group has acquired Scientific Software International, Inc.

Vector Software Acquisition, a sole subsidiary of Vector Psychometric Group, acquired Scientific Software International, Inc. expanding Vector’s statistical software offerings. Vector Psychometric Group (VPG), a leading provider of psychometric and data analytic solutions for clinical outcomes, educational, and psychological assessment, has acquired Scientific Software International, Inc. (SSI), a market-leader in statistical software for social, behavioral, and biostatistical sciences. SSI has been developing, publishing, and distributing specialized statistical software products since 1971. SSI has been a driving force behind many widely … Read More