ABSTRACT
Construct validation takes place when an investigator believes that his instrument reflects a particular construct, to which are attached certain meanings. In the early stages of development of a construct or even at more advanced stages when our orientation is thoroughly practical, little or no theory in the usual sense of the word need be involved. The laws in a nomological network may relate observable properties or quantities to each other, or theoretical constructs to observables; or different theoretical constructs to one another. A necessary condition for a construct to be scientifically admissible is that it occur in a nomological net, at least someof whose laws involve observables. The difficulties in merely 'characterizing the surface cluster' are strikingly exhibited by the use of certain special and extreme groups for purposes of construct validation. Numerous successful predictions dealing with phenotypically diverse 'criteria' give greater weight to the claim of construct validity than do fewer predictions, or predictions involving very similar behaviors.
