 The sort of statistical calibration (or “scaling”) provided by Rasch models yields repeatable results, but it is often only a first step towards full-fledged psychological measurement. Psychologists are typically interested in the results of a measure not for its own sake, but for the sake of assessing some underlying and latent psychological attribute, e.g., English language comprehension. A good fit between item responses and a statistical model does not yet determine what the questionnaire is measuring. The process of establishing that a procedure measures the intended psychological attribute is known as “validation”. One way of validating a psychometric instrument is to test whether different procedures that are intended to measure the same latent attribute provide consistent results. Such testing belongs to a family of validation techniques known as “construct validation”. A construct is an abstract representation of the latent attribute intended to be measured, and 