Validity Generalization as a Continuum

Tett, Hundley, and Christiansen (2017) make a compelling case against meta-analyses that focus on mean effect sizes (e.g., rxy and Ï ) while largely disregarding the precision of the estimate and true score variance. This is a reasonable point, but meta-analyses that myopically focus on mean effects at the expense of variance are not examples of validity generalization (VG)—they are examples of bad meta-analyses. VG and situational specificity (SS) fall along a continuum, and claims about generalization are confined to the research question and the type of generalization one is seeking (e.g., directional generalization, magnitude generalization). What Tett et al. (2017) successfully debunk is an extreme position along the generalization continuum significantly beyond the tenets of VG that few, if any, in the research community hold. The position they argue against is essentially a fixed-effects assumption, which runs counter to VG. Describing VG in this way is akin to describing SS as a position that completely ignores sampling error and treats every between-sample difference in effect size as true score variance. Both are strawmen that were knocked down decades ago (Schmidt et al., 1985). There is great value in debating whether a researcher should or can argue for generalization, but this debate must start with (a) an accurate portrayal of VG, (b) a discussion of different forms of generalization, and (c) the costs of trying to establish universal thresholds for VG.