“Usefulness” in psychometrics

“Consider, for example, instrumentalism. This view does not invoke truth but usefulness as the primary criterion for the adequacy of scientific theories and measurements. However, we are surely not seriously considering the idea that we have to rule out rivals to the hypothesis that intelligence tests are useful. The Wechsler Adult Intelligence Scale (WAIS; Wechsler, 1955) comes in a big heavy box, which is very useful to hit people on the head with, but the hypothesis that the WAIS is valid for inflicting physical injury is certainly not the kind of hypothesis we are interested in.”

Borsboom, D., Mellenbergh, G.J., & Van Heerden (2004, p. 1065).  The concept of validity. Psychological Review, 111, 1061-1071.