Keith Marcus congratulates Almond et al. on an interesting article bringing together two topics that are important to the field of testing. He states that some aspects of the exposition came across as not yet fully developed, as if the manuscript had been hurried to press. In this commentary, he attempts to expand aspects of the article, which he…

In a series of articles and comments, Kenneth Bollen and his collaborators have incrementally refined an account of structural equation models that (a) model a latent variable as the effect of several observed variables and (b) carry an interpretation of the observed variables as, in some sense, measures of the latent variable that they cause.…

I congratulate Paul E. Newton on a thoughtful and evenhanded contribution to test validity theory. I especially appreciate the evident care that went into interpreting the various authors whose work Newton discusses. I found many useful insights along with the few minor points with which I might quibble. I comment on three aspects of Newton's…

The commentary has greatly enriched the discussion initiated by the three target articles. The distinction between constructs and concepts contributes to both the top-down and bottom-up aspects of the dialectic between measurement theory and practice. The distinction also illuminates the abstraction from observation to manifest variables. However,…

A theoretical variable such as integrity, conscientiousness, or academic honesty may correspond to either a construct or a concept, but the standard idiom does not distinguish the two. One can describe the difference between constructs and concepts in terms of set theory. Constructs extend over actual cases, whereas concepts extend over both…