R. Darrell Bock

We are sad to relay news of the death of R. Darrell Bock. Darrell was a titan in the field – his work defined the shape and trajectory of modern psychometrics. We each had the pleasure of meeting Darrell at various points in our careers and he was as impressive in person as he was in his published work. All three of us – indeed this entire company – have been shaped by Darrell’s many contributions. We echo the closing … Read More

Announcing the Release of IRTPRO™ 5.2

VPG is pleased to announce the immediate availability of IRTPRO™ Version 5.2 which includes an option to import current Excel spreadsheets (*.xlsx) in addition to older Excel spreadsheets (*.xls extension). Users holding active IRTPRO™ subscription licenses are encouraged to upgrade, by logging into their account on the VPG Store and navigating to the License Detail record under My Account – Licenses – Manage.

Celebrating 50 Years of Structural Equation Modeling with LISREL

Scientific Software Inc., a wholly-owned subsidiary of Vector Psychometric Group, LLC, has released LISREL 11 on 06/24/2021.  The substantially upgraded new version marks the golden jubilee of a seminal development in the history of Structure Equation Modeling (SEM).  A little over a half century ago Professor Karl Jöreskog published a monograph in the Educational Testing Service (ETS) Research Bulletin series, entitled A General Method for Estimating a Linear Structural Equation System. The technical development was supported by the availability of … Read More

Announcing the release of IRTPRO™ 5.1

VPG is pleased to announce the immediate availability of IRTPRO™ Version 5.1 which includes bug fixes and a new ICC/TIF plot display control option in both the Advanced Options dialog and command line syntax. Users holding active IRTPRO™ subscription licenses are encouraged to upgrade, by logging into their account on the VPG Store and navigating to the License Detail record under My Account – Licenses – Manage.

VPG releases flexMIRT® Version 3.62

VPG is pleased to announce the immediately availability of flexMIRT® Version 3.62.  Version 3.62 fixes a bug with multiple-group IRT modeling, and a labeling issue in output delivery. Importantly, Version 3.62 uses a completely new pseudo random number generator (PRNG), replacing the one that has been in use since flexMIRT 2.0.  The new proprietary PRNG is based on the popular Mersenne Twister 19937 generator that substantially outperforms the PRNG used by flexMIRT previously.  They will lead to slightly different results … Read More

VPG RELEASES FLEXMIRT® 3.6.1

VPG is pleased to announce the availability of flexMIRT® Version 3.6.1, which can be obtained through our webstore. The new version fixed several bugs with data import, nominal categories models, and cross-classified models. It also improved the support of covariates in MAP scoring for single level models.  Users running version 3.6 are encouraged to upgrade at no cost.

VPG Releases flexMIRT® 3.6

VPG is pleased to announce the availability of flexMIRT® Version 3.6, 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.

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 irtpro.com to find out more about IRTPRO™.  Visit our storefront at store.vpgcentral.com to learn more about licensing and to make a purchase.