Our Portfolio

In addition to authoring the software used by ETS to perform vertical scaling, we authored the IRT calibration software used at ETS for the GRE, GMAT, and TOEFL testing programs. We also contributed a significant portion of the software employed to assemble and evaluate item pools at ETS for these programs. It was here that we first pioneered our posterior-based analysis methods, and in particular our option curve analysis methodology. In our experience here at Tamabilt we have found that there is a tendency among even the most experiences consumers of IRT methodologies to treat the calibration of items as nothing more than the process of obtaining IRT parameter estimates. When we first introduced our graphical presentation concepts at ETS and again at ACT we were first met with skepticism, and among the old-guard psychometricians there was a tendency to reject our approach without further considerations. However, among the test development staff we gradually found acceptance and eventually tremendous enthusiasm as the value of our approach was discovered through experience.

For ACT we invented the patented scripted testing algorithm now used by GMAC for the GMAT. Pool assembly, pool evaluation, and item calibration for the GMAT are all currently performed using our software, which again employs our posterior-based methods of analysis. First and foremost, our approach stresses the evaluation of items and feedback to the item writers and editors over the mere characterization of how an item functions statistically. Toward that end it is essential to view the resulting set of IRT item parameter estimates as only one of several important outcomes of the calibration process. That perspective is evident in the Tamabilt calibration output report.

For one of our most recent clients, Knewton, Inc., we authored software to perform simulations using their adaptive testing algorithm, as well as the software used by Knewton for item calibration. Currently we provide all of their psychometric operational support work. Visit the Knewton website at www.knewton.com and learn about their amazing new algorithms for adaptive learning.

We also provide IRT and equating expertise to the very capable crew at the Buros Center.