This paper follows a line of logical argumentation to claim that what Samuel Messick conceptualized about construct validation has probably been misunderstood by some educational policy makers, practicing educators, and classroom teachers. It argues that, while Messick's unified theory of test validation aimed at (a) warning educational…

The vertical scales of large-scale achievement tests created by using item response theory (IRT) models are mostly based on cluster (or correlated) educational data in which students usually are clustered in certain groups or settings (classrooms or schools). While such application directly violated assumption of independent sample of person in…