The purpose of this paper is to propose a revision of the well-known Campbellian system for causal research. The revised system, termed the COPS model, applies to both applied and basic research. Five validities are included, where two validities are adopted from the Campbellian system, and the validities are partly hierarchically ordered.…

The purpose of the present paper is to critically examine causal inferences and internal validity as defined by Campbell and co-workers. Several arguments are given against their counterfactual effect definition, and this effect definition should be considered inadequate for causal research in general. Moreover, their defined independence between…

Accounts for the paradox posed by F. Lord (1967) concerning the logic behind statistical adjustment with preexisting groups in both causal and descriptive terms. The account of the paradox illustrates the need for causal metamodels. (Author/SLD)

Based on the division of attained change for each treated individual into causal and noncausal change, the product-moment correlation between causal change and initial level is studied and compared with the correlation between attained change and initial level. Relevant formulas for true scores at population level are presented. (SLD)

Four general criteria are proposed for the choice of a metrical solution for a causal effect: (1) compatibility with the effect; (2) ease of communication; (3) lack of measurement error bias; and (4) stability across subjects and situations. These criteria are illustrated for randomized and nonrandomized designs. (SLD)