Confirmatory Factor Analyses of Multitrait-Multimethod Data: Many Problems and a Few Solutions

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Abstract
During the last 15 years there has been a steady in crease in the popularity and sophistication of the con firmatory factor analysis (CFA) approach to multitrait- multimethod (MTMM) data. This approach, however, incurs some important problems, the most serious being the ill-defined solutions that plague MTMM stud ies and the assumption that so-called method factors reflect primarily the influence of method effects. In three different MTMM studies, ill-defined solutions were frequent and alternative parameterizations de signed to solve this problem tended to mask the symp toms instead of eliminating the prcblem. More impor tantly, so-called method factors apparently represented trait variance in addition to, or instead of, method var iance for at least some models in all three studies. Further support for this counterinterpretation of method factors was found when external validity crite ria were added to the MTMM models and correlated with trait and so-called method factors. This problem, when it exists, invalidates the traditional interpretation of trait and method factors and the comparison of dif ferent MTMM models. A new specification of method effects as correlated uniquenesses instead of method factors was less prone to ill-defined solutions and, ap parently, to the confounding of trait and method ef fects. Index terms: confirmatory factor analysis, construct validity, convergent validity, correlated uniquenesses, discriminant validity, empirical under- identification, LISREL, method effects, multitrait-multi method analysis.