My PhD program in experimental psychology focused on measurement, and even though content is always important in test development, I’ve put special focus on ways to structure, administer, and score tests to obtain as much useful information as possible in a reasonable time. Early in my career, I had the good fortune to work with Colin Elliott, who in the 1970s had developed one of the first clinical tests based on the Rasch model (a form of item response theory), the British Ability Scales. In creating the US version (Differential Ability Scales), we were able to make additional innovative applications of Rasch scaling, especially in adaptive and out-of-level testing.
Throughout my career, the Rasch model continued to be an important tool in developing diverse types of tests in cognition, neuropsychology, educational achievement, early childhood, speech/language, and behavior. Two decades ago, it was the basis for Growth Scale Values (similar to Woodcock’s W scores), which were originally designed to measure growth in school achievement, but which have also proven to be very useful in other change-oriented applications such as clinical trials. Currently I consult with Pharma researchers on behalf of Pearson to help them measure change most effectively, especially by using GSVs.